I am in the middle of developing a social networking application for a very select user niche which could scale to a few million users. Right now I have always hosted applications on RackSpace Cloud and I have no issues with them at all - always been a really good service and never had any downtime.

My question is though does anyone think that cloud computing is not the way to host scalable web apps? Or can anyone with experience of this recommend a better solution.

I have always shunned trying to run big servers from my own facilities as I think it seems silly to go to the expense of bringing in big alternative power supplies and all the other necessary precautions when other companies already do this. I looked at managed hosting services but this proved to be a bit too expensive for us at the start and the scalability of it wasnt good enough - it would take a day or two to get a new server provisioned. Therefore I ended up on a cloud platform.

If anyone has any recommendations or advice it would be greatly appreciated.