Two officers from the force have been retired or resigned from their posts following issues raised by their actions on social media.
One high-ranking West Mercia officer, shown to be an inspector or above, was disciplined for discussing information about a police investigation with friends online.
A constable was also given a final warning for "inappropriate association with a vulnerable person through personal social networking site".
Of the 19, 17 faced action of some form, with only two having the investigations against them dropped.
The force works in partnership with Warwickshire Police, which also had eight investigations made about members of its staff due to their use of social media.
Dyfed Powys Police also received four complaints, with one employee with accused of being "threatening, bullying and intimidating towards a complainant by sending private messages via Facebook".
All forces across England and Wales are now being instructed to create a code of conduct to ensure both police officers and civilian staff do not misuse social media.
Abigail Hartley, a spokeswoman for West Mercia and Warwickshire Police, said: "Social media has revolutionised the way people communicate and share information and provides both forces with new and innovative ways of engaging with and involving people in policing.
"As with anything there are risks attached to information sharing, however the forces believe these should be proportionately and appropriately managed by the same principles that underpin all police activity.
"The basic principle is that all officers, staff and volunteers are accountable for whatever they put into the public domain even in a privately held account and must not behave in a way which is likely to discredit their police force.
"This applies to information published via social media both in a professional capacity and for private social media usage by officers, staff and volunteers and even their families where the information may have been obtained from the officer, staff or volunteer.
"All officers, staff and volunteers are reminded that any comments made on social media will be deemed to be in the public domain and seen potentially as official police comment.
"Any inappropriate comments are dealt with by internal misconduct procedures. This applies to both personal and corporate sites. "
Hundreds of police employees have been investigated for breaching social media guidelines at forces across England and Wales during a five-year period, according to documents released today.
Nationally, a total of 828 cases were reported to police bosses, ranging from social media gaffes to sackable offences.
About a seventh of all investigations resulted in no further action or the personnel having no case to answer.
This compared with around a tenth of cases ending in a resignation, dismissal or retirement.
Greater Manchester Police reported the most investigations with 88, followed by West Midlands with 74 and the Met Police with 69.
Star comment: The perils of social media use
West Mercia Police draw up social media guidelines:
West Mercia Police today revealed it is one of a number of forces that have drawn up policies to guide officers in how to use social media properly.
Sites such as Facebook and Twitter have become useful tools for police to launch witness appeals and keep the public informed.
But some employees have also fallen into the trap of using personal accounts in a way which has raised issues with the general public.
The force has an online social media policy, which aims to guide its officers in how to behave properly when online to reduce the number of incidents.
Abigail Hartley, spokeswoman for West Mercia and Warwickshire Police, said: "Ultimately, social media is another channel for officers and staff to engage with the public. They are trusted to use it in the same way they would speak to a member of the public on the phone.
"The risks attributed to using social media should not inhibit or prevent Warwickshire Police and West Mercia Police maximising the opportunities social media provides.
"Warwickshire Police and West Mercia Police use social media to engage with, motivate, inform and educate our communities to better protect people from harm.
"To enable our workforce to effectively use social media both forces have a Social Media Communications Policy and set of guidelines which inform our officers, staff and volunteers how to use social media in both a personal and professional capacity.
"We also actively encourage our workforce to follow the national ACPO Guidance on the Safe Use of the Internet and Social Media by Police Officers and Police Staff."
The force's policy has been created under its strategic partnership with Warwickshire Police and has therefore been designed to cover staff at both forces.
West Mercia's policy states: "Warwickshire Police and West Mercia Police will use social media to engage
with, motivate, inform and educate our communities to better protect people from harm.
"The outcome we seek to achieve is that every day we want people to be discussing, debating and endorsing the work of Warwickshire Police and West Mercia Police online.
"We must recognise the vital importance of participating in online conversations
and be committed to ensuring that we take part in social media in the right way – not only as a broadcaster but as a participant listening and responding to both the
positives and negatives.
"All officers, staff and volunteers must note that any comments made on social media will be deemed to be in the public domain and seen potentially as official police comment.
"Any comments could therefore be liable to a misconduct severity assessment.
"This applies to both personal and corporate sites."
The force also adds its plans to maximise its opportunities through social media by "Trusting and supporting our workforce to engage in a professional and appropriate manner, in accordance with our joint force guidelines, with the public every day through this channel.
"We will engender a culture of openness, honesty and accountability through social media and in relation to its use."
The officers are also encouraged to follow ACPO guidelines, which states officers and police staff should avoid using the internet while off-duty or after having drunk alcohol, due to the potential for their judgement to be impaired.
They also warn of the propensity for criminals to trawl the internet and identify personal information about police employees "with a view to embarrassing, discrediting, harassing, corrupting or blackmailing them or their families for their own benefit".
It adds: "It is recommended police remove personal details from the edited electoral roll, ensure telephone numbers are ex-directory, ask Google maps to remove pictures of their house, car or persons."
Police have also been warned about responding to trolls - internet users who goad and bully others into responding with hurtful or ignorant comments.
Despite the strict policy, 13 officers and six members of staff at the force have received disciplinary action due to inappropriate behaviour online.
Three faced action for accessing social media sites while on duty.
While eight were disciplined for putting up inappropriate comments or content.
Three officers of the Sergeant rank faced action, while one was of inspector grade or higher.
Dyfed Powys Police also received four complaints against staff or officers for their action online.
The force also has a published social media policy, which encourages everyone interacting with them online to follow "Netiquette" - a series of rules about appropriate use of social media.
Rules include only posting something online that you would be happy to say in person, being selective on the information posted and refraining from personal abuse.