Here is my 2 cents. There is a risk of harm housing leopard geckos together. One may accidently bite the other thinking a tail is food. There may be a bullying issue. People have differing opinions as to how great that risk is, but it's hard to deny that it exists.
The only good reason I can see for putting multiple leopard geckos together is to breed. Even then, there is a calculated risk, but to get more leopard geckos it is a reasonable risk to take. If you just want them together because two leos together seems cooler than one by itself, I would advise against it, although it is ultimately your choice. Also, as Elizabeth said, it is hard to notice subtle signs that something may not be right if you do not have experience with the species. If you do opt to house leos together, you should be prepared to seperate them at the first sign of a dangerous situation. Just my humble opinion.