I know that there are people trying to get ps3 playing backup games as I type and I hope they can do it as soon as possible. And I think that Sony should hope for this too.
Ps3 is one nice looking and nice specs piece of hardware for anyone that likes gaming, have a powerful media center and web browser on the living room. But when you buy a PS3, your first objective is play games! Thare are lots of people (like me!) that prefer to buy games they like but most of the people don't like to pay for games and their developers.
Of course they prefer to have Xbox 360 because of that. That is the major reason Sony can't sell as mutch as 360, PS3 will stay on Stores because of that. The ideal thing is that no console can run backups. If you want to play, pay for the work and investment made by it's developers.
But if you have only one console that run backups the war is not fair for the others and the statitics will show that. I have to say, PS3 will lose this battle (console market) because of this factor, the other players are cheating! The intension of sony it the best, the right way to foolow, but maybe it's not the right moment because of the microsoft politics: "let almost everyone use our software for free because that make us popular", smart guys there... Good luck dev team!
Well, being able to play backups on the PS3 (which i actually hope it will be possible soon) can lead it's sales to two ways. It can turn out as a bad thing for sony, since they will lose money on software sales. On the other hand it can help the hardware sales to rise, because it will encourage people to buy a PS3, knowing they will save money on games.
I'm pretty sure the PS2 did great sales-wise, because people knew it could play backups. I think hardware sales is a bigger factor then software sales. The biggest losers will be the game developers/company's.