My current startup has a 9-5 culture, and we get a lot more done than any other startup I've worked for. No ping-pong, no long lunch breaks, no watercooler discussions, much less surfing on company time. I get more done in 8 hours than I used to get done in 12, and I get an extra 4 hours with my family.

I find that ping-pong and watercooler discussions are necessary as breaks. Otherwise you burn out and you only get, say, 4 hours of real work done in an 8-hour day.

Breaks are still necessary, but they're a lot less frequent and a lot shorter.

Fair point, my HQ is in NYC I can attest to the 9 to 5 as well. I think it has more to do with transit scheduling than anything. Then again Paris is extremely expensive to live in the Metro area as well so that may have something to do with my experience as well.