Originally posted by yoshi
Just thought I'd correct you on this, you might as well know what you are pirating if you're going to do it!
TMD is not a type of movie, it is the name of the group of people that rip and distribute their movies. I'm quite sure they use the DivX codec most of the time. They are lower quality because of two things: their movie sources are of lower quality (nearly always cams and telesyncs), and their encoding bitrates are quite small (as well as resolution). All of this results in a shitty (but first, which is important to some people) rip.
When you say you wait a month or two for it to "go divx," what probably happened is that a ripper (who is a member of one of the groups) got their hands on a screener or dvd copy of the movie, and (because of the higher source quality) they ripped it at a higher quality.