There are already two:
- CKG (crypto-kingdom gold) - rpietila explained. And you don't need to play. You can 1) just deposit and wait 2) hire a wealth manager which will (hopefully) optimise your profits for a fee
- Cryptocoins-dice.com (investing, not gambling). The admin is legit, I have his phone number and I'll get his ID, we talked a lot and will physically meet (as well as a lot of other Bitcoiners to testify) on the 30th of March. Estimated APR (based on statistics for just-dice): 50% Sure, as long as multisig is not implemented in Monero, there are risks. Not that other assets like GAWminers are better.
Rpietila told that it is better to play the game not only invest and I understand this very well.
Virtual casino surely absorbs coins but on the other hand it may not be a kosher way of making money?
The better way to make money is to organize and exchange that has ability to borrow USD/XMR and trade with leverage. I am already every now and then lending my bitcoins in Bitfinex so this type of business is interesting.
Also some kind crowdfunding site (such as btcjam) - however this requires a lot of bad loans before there is enough data for regressions on the dependency of any variable and ability/willingness to repay.
Different kind of Monero ventures started by trusted person are also interesting however I am a bit conservative in this.
Creating Monero economy is the challenge obviously... However, this is something that might make Monero unique. If I am not mistaken, bitcoin do not have that many investor type of demand but more it is marketed as a tool to do day-to-day transactions.
Just my 2 mXMR after long day of working and studying.