Anyway, go look at the Steam hardware survey. Most people don't have a connection that's fast enough to support this kind of service. Many of those who do, like me, have bandwidth caps that would severely limit their gaming.
There's also the question infrastructure for the service. You could have a 500 Mbps connection that's worthless for the service is if you're too far from a data center and have a high latency. You would need a ton of servers before you could roll this out worldwide. I live in a big city in the US and can play OnLive fine, but Gaikai's beta wouldn't let me connect due to my latency. It's going to be a very long time before it's feasible to do something like that. There are likely to be 50 dumb anti-piracy schemes to worry about before it's even possible to think about it.