My brother and his wife do this. They got in on the Jetblue $10 deal last year and went to Boston. They had so much fun that since they've gone to Providence and will be in Denver next month (they're based outside Baltimore) when they find deals they like.

Personally I've only done it once (I flew a cheap Independence Air flight to IAD because I wanted to try the airline). Other than that, I will only go to cities I want to see and only on my preferred carriers unless the deal is too good to pass up.