In addition to the skill/change thing, there's something I've been told by a Linden Labs employee (when they closed the casinos in Second Life) is that there's

In addition to the skill/change thing, there's something I've been told by a Linden Labs employee (when they closed the casinos in Second Life) is that there's a specific provision for "game tokens" versus real money. That is, as long as all you can earn from gambling is tokens the government doesn't really care. Casino chips, however, are basically proxies for money and thus cannot be considered game tokens.