Cloud service is unrealiable at best. Plus you are fully depending on a certain vendor and their ability. Both in terms of security and backup.

Its one of those buzzwords and ideas that will die again.

At best cloud computing can be used for some non important personal stuff.

Another issue is the datacenters to support it. They need to be localized and in reality using more resources than you would elsewhere.

Its like trying to make everyone use terminal services...