Now I know what you are thinking from the title. Isn't investing in Bitcoin basically a gamble as it is? Well, yes, yes it is. However, one day it may magically stabilize so that it doesn't fluctuate by more than $10 a day. Bitcoin would probably not be an ideal mechanism for online gambling even after this. Let's say we had some random online gambling site like WeLuvBingo.com. What would happen if they started accepting bitcoin?
This in theory could sidestep all sorts of legal frameworks to explicitly forbid online gambling(with "real" money) in the US and other countries. Bitcoin is inherently not anonymous though! The US government at least has already started cracking down on people who buy drugs with bitcoins. It probably wouldn't be too hard to do the same with gambling sites. Bitcoin works by a ledger, which is publicly readable. If someone knows your bitcoin address, they can see what addresses you send money to. However, there are some crazy sketchy looking websites that "combine" transactions, obscuring where your money goes. One such site is bitlaunder (hey, I told you it sounded sketchy). With the way this happens, it makes it nearly impossible to trace the bitcoins to you.
But, aside from the non-anonymous issue, there are plenty of other issues. Using bitcoin for gambling would require confirmations. Once you require a confirmation, suddenly it takes around 10 minutes to get your money into the service. That's quite a let down. If they didn't do confirmation, they'd be vulnerable to double-spend attacks where people could gamble with already spent bitcoins... If they managed to do it fast enough, they could then "cash out", taking their winnings without ever having put a single penny at risk. This of course is not nearly as easy as it sounds, but it's possible.
In conclusion, bitcoin is awesome for some things. Probably not for gambling though(unless you mean "speculation")... at least not with the current version of bitcoin anyway.