not to mention that online gambling is not legal in many jurisdictions!
Good point, Online gambling owners tends to avoid this regulations and tax paying but the thing is that this people behind the online casinos are respectively paying some officials just to continue it's operation. It's a fact, This practices were made mostly in the Asian countries. Though, the hype of Bitcoin has started so this illegal Bitcoin casino owners are now prone to being shut down especially when it's user are growing each day, to the fact that it is now noticeable.
There are no regulation/s yet for this Bitcoin Casinos. A government can't regulate the transactions done thru Bitcoin, so technically speaking Bitcoin casinos are some what invisible to the Government.