In my day-to-day git workflow, I have many topic branches, like so:
o--o--o (t2) / o--o (t1) / o--o--o (master)
Don't rebase. Start your features from a common point. Merges are way less work in the end.
This is what we do:
http://dymitruk.com/blog/2012/02/05/branch-per-feature/