[eeeeeeeeeeeee]

I've run my own dns infrastructure for a medium sized company. It could get attacked. And you better be sure your providers are OK with the bandwidth usage or they will shut you down. You could be down for hours. If you are targeted it could be very bad.

Amazon and providers like Dyn have Anycast so routing will normally be faster than what most companies would want to spend on their own dns systems. And they can absorb most large attacks. Not to mention that uptime for route 53 is near 100% usually and is pretty cheap. I don't think you could build something cheaper for yourself that offered similar features to route 53.