Valve seems to be moving away from the traditional approval process for what games get to be sold on Steam and what games do not.
Using the Steam community to let potential buyers say what games they might be interested on spending their cash on.
I suppose this makes the process of selecting game a lot more reliable. If a game makes its way there its a guarantee that people are actually interested in it and should also help developers with another (huge) venue to get feedback on what is needed to make their game more interesting to people and get them to buy it.
Also it's coming soon...