[toast0]

Using multiple providers for mostly static DNS is easy, pick one as primary and AXFR to the other and notifications and whatever. Or it's not too hard to keep a zone file in source control and sync it to the providers.

Using multiple providers for fancy DNS, like only providing IPs that pass healthchecks or geotargetting users to datacenters gets pretty hard, because the different providers have similar capabilities, but no uniform interface, so you've either got to do it manually, or you have to build out your own abstraction that is probably limiting.

If possible, insourcing DNS makes the most sense to me, because if you can't keep your service online, it's not the worst if your DNS is offline; and if you can keep your service online, you probably won't mess up your DNS too badly.

[jfoutz]

So much this. Keeping feature by feature parity is the tricky part.