One of our clients had suffered from a trademark breach on Twitter, where one of their former employees had set up a Twitter account for their company with his personal email address, and when he left, so did their Twitter account, which was still live, and still available to search on the internet.
It is so important when managing a social media presence for your organisation that it is done through a work account, and that control is held by senior management. That way, in case employees leave the organisation, you can still maintain control of your company profiles, and keep the reputation of your company firmly in your hands.
However, in case you are or ever do suffer from Trademark issues, you can apply to Twitter to make contact with the account holder and regain control over the account. Word of warning, it may take a while, as Twitter-ers do some investigating, plus they have to get a response from the account holder before they can act.
Here are the links you need:
Twitter’s trademark policy