What is your opinion on it? I've noticed that Flea does this all the time when he plays. I even started doing it myself when I play, I hope it's not considered a bad habit. If you're climbing down strings, it's excellent because your finger is already primed and ready to rake down. I've noticed it produces an excellent sound too. It has KILLED my speed playing though. Here's a good video showcasing the technique. Notice how his finger bounces back against the E string every time he plucks, that's what I'm talking about.