There are lots of topics popping up on this thread.
Anyone who thinks the pro MTB scene is purer, google Filip Meirhaeghe (the biggest star in the discipline) and you'll find an EPO positive and admission in 2004 or 2005. I have to concede that I don't follow MT biking, so I'm not aware of other cases. 5 years ago though, there weren't any drug cases in Major League baseball.
I find that the only proof anyone can seem to muster up concerning Armstrong doping is the fact that he beat a lot of riders known to dope. That 'proof' belongs more in the realm of belief rather than objective fact, but have it your way. Considering the French gov't, ASO (the group that operates the Tour), WADA, newspapers, muck-raking authors and probably more have spent most of 7 years relentlessly trying to prove Armstrong doped, you'd think there would be something more convincing than he must have doped because he won. As for the guilt by association approach, it's not very effective in light of the fact that US Postal/Discovery have never had a doping positive/drug bust. Frankie Andreu admitted he doped in 1999 while on US Postal. That's it! The former teammates who have been busted, got busted on other teams after a significant improvement in results from their Postal days. See what Landis, Hamilton, and Heras won in Postal colors compared to post-Postal.
Did Armstrong dope? I don't know, but I'd hate to have to conclude that greatness=drug cheat.