Academia.edu is a new social network(ing) site for academics (TechCrunch). Should you add this to your busy SNS life? To a limited extent.
The academic community would definately benefit from a dedicated SNS, after all, our needs are very different from the general user and the business user. However, I found Academia.edu to be extremely slow and not particular user-friendly.
In its current state, spending hours on your Academia.edu profile could very easily be wasted. If they improve on the speed and the user-friendliness, however, it could definately be a useful site. Solution: just put up a basic profile for now, and wait to see if it improves and how much interest it generates. If you really are desperate to waste a lot of time on another SNS, then jump into the Hoff’s; taking pointless SNS to their logical extremes.