So your company started using social media. Twitter for all those tweeting followers and Facebook and Google+ for the company loving fans. Thousands, maybe even hundreds of thousands of people following your well-crafted messages. Until that moment you find out someone posted a bad message on behalf of your company name.
Most services, including Twitter and Facebook consider accounts as single users. For small or medium sized company this might be indeed a single user. In a big company like a multinational, chances are high that several key contacts are appointed, to speak in the name of the company. Usually this will be your people from the communications or PR department.
Like every single individual has to protect their account, a company has to protect their online presences. With several people having access to the same account, you might want to consider additional care and protection to protect the keys of the kingdom. Tips include using a strong password to the main accounts, with additionally software on top which manages this account. For example Hootsuite provides the possibility to allow team collaboration. If one of the colleagues decides to work at another company, disabling that particular account is enough. No more ad-hoc password changes or risking a bad last post or being locked out to your own company account. Consider all the time and hassle to get that rectified.
Protecting against bad links is a second step. Where shortener services like Bit.ly help you in saving space in tweets and providing valuable analytics, it could also risk your own people in opening malicious sites. Especially since you are online with your company presence, it might be prone to phishing attacks. Decide on how and where to respond to messages. Additionally create a social media policy on how to deal with this fairly new PR tool and its risks.