Having to manually shard your data seems like so much work when offerings like App Engine will take care of that for you. It seems like exactly the kind of thing that you shouldn't have to think about when you're trying to get a business off the ground.

I can see the lock-in concerns with AppEngine, but an AppEngine level of abstraction seems so much more appropriate than manually deploying/configuring an entire infrastructure of proxies, load balancers, web servers, etc. Especially when an error can take down your whole site, like in this example.