Difference between responding to "danke" with "bitte" versus "gerne"
I hear native German speakers respond to a danke with bitte as often as with gerne.
Is there a semantic difference between the two of them? Or a usage rule behind the choice? Is one more polite than the other?
I don't think that I really see any significant difference in using one over the other, but mgoni made a point. If I made something rather unwillingly, I'd never say "gerne" as I wasn't happy to do the favor; but I still might say "bitte". If I did the favor willingly (or happily), I'd go with both equally often — I guess.
@Em1 It is better to note that if something done unwillingly, it can be also said that: **ungern**
"Gerne" as an answer to "danke" is a newer phenomenon in spoken German. I would consider it as a colloquial sloppiness, and my native feel for language always gets a little bit offended when I hear it. ;-)
Note that there are plenty of other (maybe regional) variants of how to answer *danke*, such as (mentioned in comments below) "nichts zu danken", "keine Ursache", "für nichts", "kein Problem", etc.
Aventurin is right. I can't prove it, but in my opinion "gerne" is the outcome of modern marketing strategies intending to train employees to become more customer-friendly. In fact, very often people working at service hotlines close conversation by a "gerne" with a certain intonation and (fake?) enthusiasm. Also have a look at my answer to https://german.stackexchange.com/q/56404/34192 .