I am assuming that lots of parents named their kids in honor of Hitler and wondering if anybody has ever looked into it or if any Germans might know? Also, how common was/is Hitler as a surname?
I answered a similar question regarding the Adolfs of Germany a while ago: http://www.reddit.com/r/AskHistorians/comments/1vfkq9/z/cerw00r (I'm on my phone right now, so I can't format it nicely.) The tl;dr is basically that the given name Adolf has drastically fallen out of use and is practically non-existent among younger Germans. However, there are of course older Adolfs still alive.
The surname Hitler was actually never common in any way as it was a name chosen later. Hitler's birth name was Schicklgruber if I remember correctly.