Heh, the number of times DNS has bitten me in production... My main objections to DNS are:

1) You have no control over clients, there is absolutely no rule that says clients have to respect TTLs (I'm looking at you Java)

2) We are talking about hundreds of HAProxy load balancers, thousands of clients and hundreds of backend services which are moving around all the time. I just honestly didn't want to deal with DNS propagation limiting my flexibility.

3) At least at Yelp, we don't really have particularly nice control apis for DNS. This is sort of specific to Yelp, but it was a factor.