Investing in a Game Before Purchase

So I've noticed that more companies are following a trend: getting players to invest in a game before it's even released. I started playing the Battlefield: Bad Company demo today. I had seen some articles on it and saw there was a demo so I checked it out. I like it. But there's a catch! If I can rank up to a certain rank before the game releases next week, I get an unlockable in the full version of the game!

So if I rank up to level 4 in the ranked matches of the demo, I will get an unlocked Uzi in the real game. That's some investment. I like the demo, but this incentive gives me more reason to play and if I do get to level 4, I have more reason to buy the full version. After all, I already have a gun that I earned!

Other games are also doing similar things. Fable 2 will release some gambling games on Xbox Live Arcade a little bit before Fable 2 is released. People can earn money for their in-game character by buying these XBLA games and doing well in the them.

Personally, I think these are good ideas, from a marketing stance. I love demos to begin with. They give you a real idea of what the game will be like. But with this working towards something, you are also guaranteeing not only that people will be invested but that they will continue playing the demo so that when other people try out the demo there's a lot of people to play with.