All the time. Not everyone abuses fast travel, some of us like to feel that we are still "in the world." I walk when I can't get a carriage. Unless I'm moving a bunch of crap between houses, then I speed things up a bit more.
How can anyone abuse fast travel? You either use the in-game feature as it was intended to be used or you don't use it, surely? It's like saying i abuse destruction because i use it more often than the next guy and so on...
I love how some people seem to take the moral high ground when it comes to keeping things "realistic", whilst totally ignoring the fact, that how i and others play our games, in no way or form impacts on their own game world. Shooting sparks out your finger tips isn't realistic either, but you know what - Skyrim allows your toon/character to shoot sparks from his/her fingertips.