I recently read an article online about a company asking a potential employee to sign a nondisclosure agreement stating that they would not mention their company's name on Twitter, Facebook, etc... I had never heard of this, but I have heard of companies searching their would be employess on those same social networking sites. Check out the following articles, and see if you need to change the settings on your Twitter or Facebook account while you are job searching.
Check these out:
Social Media Guidelines in Your Job Search and Workplace
Employers Look at Facebook, too