We've thought about it, but with other share buttons like LinkedIn also having some success, we're reluctant to put too many buttons on the front page...it's kind of getting out of hand.
So it's certainly not off the table, but we're trying to be extra careful about what we add. Looking at other sites with it enabled, I haven't seen a flood of +1s showing up yet, but we'll keep an eye on things to see if it takes off.