Here is a link to the article I wrote on this topic. It is a very comprehensive list of why you should not house snakes together.
And, I don't blame you for asking! I agree there is TONS of contradicting information on the internet, so kudos to you for consulting the experts instead of believing what you see on google! After all, you said that you've seen pet stores do it, and others as well. Same here; I see it all the time. But I try to educate people where possible on the dangers of co-habbing. So if you'd like some more information on co-habbing, please visit my article: