I don't know how they do it either. People posting absolutely useless messages, like a quote of a post, that's already been quoted 5 times, is just as annoying as those bad mp3s though.
I don't see how they manage to mess them up so bad. What do they DO? I mean all those weird glitchy sounds... Where do they come from? I never get them when I rip with my two cdroms (one burner one regular), even when they read really slowly, like at 0.5x if it's a bad CD. I can encode the mp3s while I use my computer regularly, and the mp3 still comes out normal. So I don't see how people mess it up... if it's underpowered systems - just don't use your system for half an hour or something, that's all.
Oh well. Free is free, so you can't really complain. Not like you paid for something and got a faulty deal.