I may be closer to a dissertation topic now, thanks to a meeting with my chair yesterday. (Conversation not guaranteed to be verbatim.)
The Chair: Do you have any interest in x?
Me: Actually, yeah. I thought about it but didn't go too far because I assumed data would too hard to get.
The Chair: X is large enough that you should be able to get it from somewhere. And I can hook you up with Contact Y, who is a big cheese of x.
Me: Well, OK then. Bring it on.
The nice thing about x is that it's not studied to death, but it is important to the administration of higher education. There's a real opportunity for good work there.
I am being a little coy about what exactly x is until I figure out more specifically what I am asking - hopefully that will be soon.