We were originally going to do this and actually did for the first two weeks when we got our lesser and spider while we waited on our rack to come in. The final decision for us was a horrific article on Balls pythons and cannibalism. It is very rare but we didn't feel it was worth the risk. Also even if they don't go to cannibalism one my not eat as often as it would if they were housed separately.

http://www.rcreptiles.com/forum/about1343.html