What do you think? Some sort of rental service could be handy for those players that just want to do a single run through a game's campaign. The mechanism could possibly be 3 or 5 day leases, with the lease starting upon the first time the player opens the game application. Price could be reduced to the ~$5-10 level depending on how new the game is. I think they'd be able to tap into a new market, since many players will not buy a game at a full 60 dollars despite being interested in it because they don't consider it worth that much. That way, the developer will at least be getting some money rather than no money, and less people would turn to pirating since the risk/reward just wouldn't be worth it with prices so low to get it legitimately.  
 
For example, I'm a Battlefield player and, having played MW2's MP at a friend's house and Medal of Honor's MP in the beta, I have no interest in either of them. I would however like to play through their campaigns, but I don't consider paying 60 dollars for a 4 hour campaign to be very fair, so I currently have purchased neither. With a $10 or even $15 lease for 3-5 days the developers would've received that money from me, rather than nothing. Currently, I would need to wait a year or two for the Steam sale, where I will most likely purchase it only at that price anyway. It would seem that both parties (gamer and developer) would win if a rental service was enacted. 

I'm pretty sure onlive does that.

I suppose that could work, they already have free weekends which rely on a similar timed usage idea.
 
Also fewer people.

" I'm pretty sure onlive does that. "

I think steam sales do a pretty good job of it too. There are plenty of games I ran through in 3 or 5 days that I got for dirt cheap then deleted.

Now that I think about it, perhaps it would be hard to manage. What price do they set the rental at? If the game is currently on sale...how does that affect the rental price? What price does a game have to drop to in order for them to remove the rental service for that game?

I doubt publishers would like that. The thing with Onlive is that it's all streamed from a server. With Steam, people would have to download the full game to their hard drive to rent it. While steam would lock you out of it at the end of the rental, there is always the potential for people to hack into it and get permanent access to the game.

Free weekends are good enough.

" Now that I think about it, perhaps it would be hard to manage. What price do they set the rental at? If the game is currently on sale...how does that affect the rental price? What price does a game have to drop to in order for them to remove the rental service for that game? "