No I don't. I will follow if they write on topics I like and if they write reasonably well. As Lorlie6 does, I comment on a hub of theirs as courtesy, although if they only have 1 or 2 hubs total on topics which don't interest me at all, then I won't even do that (as it becomes too much of a time hassle to read something I really don't want to). I don't feel any obligation to follow someone back, and likewise I would hope someone wouldn't feel obliged to follow me just because I follow them.
My reasons for if I don't follow someone are:
1. Topics don't interest me
2. Very poor use of grammar or otherwise poor writing skills
3. They have written too few hubs so far for me to really decide if I might be interested in their future work
4. (rarer) - if I notice they have started following a bunch of people at once in their hubtivity... this tells me they are just following people to get followers. Plus, they will probably keep doing it, and it's annoying when existing followers start following a bunch of people at once because then it mucks up my 'feed' home page with long lists of who they are following.