I think this is the second time I've blogged about this, but it's back in the news again: Dance Dance Revolution as a weight loss program for kids.
I used to be all about DDR, but I can't play it anymore. DDR and snowboarding were major contributors to the downfall of my knees. I'm not sure it's wise to recommend repetitive impact activities like this as part of any exercise program, let alone for weight loss.
Maybe on the lower levels where you're just walking around the pad DDR is OK, but when you get better DDR becomes a double-time, high impact step aerobics routine nightmare. It's a lot of fun, but it's also a lot of jumping and landing at odd angles. If you're already overweight the impact would just become worse I would think.
I've met two other people that also blame DDR for screwing up their knees, especially the arcade version, where you play on a hard surface with shoes on. It's even worse for your knees than the home version.
Long live Stepmania.