Just look up the EA Star Wars Battlefront 2 stuff. It's a big old mess. You pay money for crates which randomly drop items that improve the game experience.

Some people consider it gambling because you are preying on the same tendencies in people for your own gain. People also don't get any real value for their "gambling". Other people say this makes it not gambling, etc. That's a very simple oversimplification of the subject - there's a lot of articles out there about it right now.