Launching a Twitter campaign with your own, custom-built hashtag is a gamble – particularly if your organisation’s actions have attracted some opposition.

On Tuesday evening, the New York Police Department embarked on a social media-based, image-improvement venture by asking the public to share pictures of themselves interacting with police officers, badged with the hashtag #myNYPD. Explaining their plan to CNN, NYPD spokesperson and deputy chief Kim Royster said: “The NYPD is creating new ways to communicate effectively with the community … Twitter provides an open forum for an uncensored exchange and this is an open dialogue good for our city.”

The first hour or so of the social media effort went well, with people posting pictures of themselves next to smiling and cheerful looking police officers. The NYPD responded with comments such as “Thanks for the photo! Keep them coming…”

It seemed, for a moment, like this was going to be a success.

Then, in what would not come as a surprise to regular readers of Friday’s Fame or Shame, things started to go wrong for the NYPD. Badly wrong.

Occupy Wall Street tweeted: “Here the #NYPD engages with its community members, changing hearts and minds one baton at a time”, the chosen picture showing an officer swinging a baton at a seemingly unarmed protestor. User “Cocky McSwagsalot” tweeted: “The #NYPD will also help you de-tangle your hair”, sharing a pic of two officers holding a woman while another pulls her by her hair. The tweets came in a flood, many of them featuring pictures from protests, or other well-known examples of what some claimed was police brutality. By Wednesday #myNYPD was one of the highest-trending hashtags on Twitter – but obviously not for the reasons New York’s Finest social media team had hoped.

While this use of Twitter may have been well intentioned, the “worst case scenario” was probably not considered, as the NYPD seemed unwilling or unable to handle the crisis once it started going wrong. The very nature of social media means that even if you use hashtags for promotion, you don’t own them, and can’t control how they are used by others – so there will always be a chance that they backfire.