A view I get is that people think that once its "in the cloud" then its safe and you don't need to worry about it. Microsoft and the Sidekick disaster is a prime example. The Sidekick phones were supposed to have all their storage online and yet Microsoft/Danger screwed up badly enough that they temporarily lost all the data for weeks.

Maintenance and administration of all these systems might be Somebody Elses Problem but you're relying on them to actually do it properly which may not actually happen.

Nothing stopping Google, Twitter and all those other sites from turning around one day and saying nah, actually we've changed our business plan and will no longer offer X service.