Investing
I believe the biggest threat to online casinos is the current bill going through the US Senate. Underplaying this issue caused problems last year with Poker shares, and the stock of any casino with a large US player base will be very high risk for the time being. If the bill passes, the shares could plunge, if the bill fails, they should hold steady or rise (the bill is widely expected to fail to have a serious impact on the current player base in the US).
If the US decides to regulate rather than ban online casinos, the shares will become a good investment provided only reputable casinos' shares are bought.
There might be some upside in 2007 with the full implementation of the UK Remote Gaming framework.
32Red seems a good choice for the above poster, however there seem to be some issues with it's poker partner.
Shares in a good poker operation should complement shares in a good casino. It might be worth looking at companies launching online skill based gaming, where players play casino type games, but against other players in competition for a prize pot rather than against the house. Such online sites already exist. I have heard of online Chess rooms where players bet against each other in head to head games - some say this will be the next revolution beyond Poker.
Investing in shares is another form of gambling, but with an element of skill, such as in Blackjack. Here in the UK, it is possible to take an interest on the financial spread betting exchanges. Although no dividends are paid, and you don't own part of the company, gains from capital movements in the share price are tax free as they are taxed as gambling winnings (no tax to pay!).