RobAnybody: I was left with the impression that a double hane is not a strong move, maybe because I've mainly seen it going wrong when played on the first line:
Addition: Umm, yeah, the corner group here is dead, which was not my intention. I'll alter it a bit. -- Rob
KarlKnechtel: I am slightly ashamed to admit that in my earliest attempts at go, GnuGo would catch me with this fairly often - and the ko didn't even occur to me - bye bye four stones.
HolIgor: Double hane is usually used to get ahead. More often on the third or fourth line. It is a strong move but requires a little bit of reading. There is a cutting point, so there is some danger.
As for this particular example, black group in the corner is dead. The side that is trying to kill usually plays solid. Attacking you don't want to give your opponent a free forcing move. In such situations double hane is unlikely to be a good move.
ChrisSchack: Well, dead unless there's something nearby to connect to, then it's ko for life (bent 4 in the corner).
Chris Hayashida: This isn't bent four. It's just plain dead if you just extend.