Given that a lot of my work-related rants on LJ refer to my boss as "scumbag boss", hell no.
Actually, even if I had a boss that I got on with, I wouldn't friend them. If only because it's great to have a place to rant where there is little chance of it getting back to them, thanks to friendslock. I haven't friended my family for much the same reason - they know I've got an LJ, they read the public posts, but I'm not giving them access to my locked posts where I do let off a bit of steam from time to time. There are a few posts there that would offend or hurt them, and I'm not going to do that...