Social Networking in the workplace needs to be treated carefully. I won't claim to know a whole lot about the capabilities of MySpace, FaceBook, Twitter, or the many other available sites out there. But more and more the presence of your overall online profile will be coming into play in either your job, or your attempts to obtain a job. I cannot say that I have ever been influenced by someone's online presence enough to stop me from extending an offer of employment, at least not yet. I can see that eventually becoming a regular part of pre-employment due diligence though. Here is an article that offers some boundaries for both employees and employers.
The six commandments of social networking at work