I've been working at Google, and had a similar experience. But I do think in many cases you can actually do better. It's not that you're smarter than Amazon/Google/... engineers, it's that you're solving a problem that it's orders of magnitude easier.
Your start-up is probably not dealing with setting up & maintaining 200K servers as Amazon, so up to a limit you can actually be better going on your own.
Yep, that was my point with the 'handful of servers' line.
But even that is pretty darn hard. You still have to deal with split brain situations, do all the right things in those cases etc.. If you are a tiny startup that isn't going to hire a dedicated sysadmin (very few of which can build that type of thing without buying some expensive hardware) then EC2 is probably a better choice.
Even just the hardware costs make it pretty braindead. We just shut down the dedicated three system setup I built because it just didn't make sense financially, and that despite me spending a month learning the intricacies of heartbeat it still had odd failure scenarios that we don't experience with EC2. Again, I'm just not that smart. :)
Your start-up is probably not dealing with setting up & maintaining 200K servers as Amazon, so up to a limit you can actually be better going on your own.