While some businesses have tried to address the inherent dangers of social media sites like Twitter and Facebook by blocking all access to those sites on their corporate networks, many are finding that to be an imperfect solution.
First, there are legitimate reasons for some employees to have access to these sites, particularly marketing and customer service departments who should be monitoring your online reputation. Second, with smart phones in so many pockets, there are many ways for workers to access these sites outside company resources.
So perhaps an alternate solution to an outright block of social media is to create a solid Social Network Security Policy that goes along with your existing Acceptable Use policy. (And you DO have one of those, right?)
Here’s an article with some tips on how to develop such a policy.