One problem with running a game that is so dependent on scripts is that one can easily fall victim to a rogue script - or a malformed one. While I'm pretty sure SL's system offers adequate protection against script attacks, I also believe that its error trapping is not near as robust as it needs to be. By that, I mean that it is next to impossible to affect one's computer outside the SL environment with a rogue script; however, crashing is certainly possible. I have found myself crashing more often when around certain avatars, but I believe it's purely accidental. Then again, there have been times where I could single-handedly lag an entire sim just from all the scripted objects I'd be wearing
All the same, however - I do not recommend running Second Life using a computer account that has automatic elevation to admin privileges. I recommend only running it from within a Windows XP/2000 normal user account, a Windows Vista account with UAC enabled, any Linux account, and any Mac account that uses sudo-based account elevation -- and
never log on as root!