I think the most common thing that people on cos.com who wear contacts even say about it is that people neeeeeed to see an eye doctor and shouldn't buy from places that don't check prescriptions.
Hm. I thought I'd seen one of these threads before. http://www.cosplay.com/showthread.php?t=166105
is another thread on this topic, but I think this one is in the right location. Idk if there's info there that isn't here that you might want to add in. ^^