Sure, but aren't all cloud services notoriously expensive as you scale? At some point I assume you'd do what companies like Dropbox and Basecamp did, and re-host some or all of it.
Well, yeah, but now it starts being totally ridiculous.
For small projects the cloud is not needed, and a lot of effort that won't pay off. The only case where it'll pay off is if you "go viral" and rapidly need to increase capacity.
This is not free. While the cloud helps with scaling, your application still needs to support it. So there's a development cost to it, even when starting.
Then, if you scale, the cost makes it almost a necessity to rapidly get back off of the cloud ...