This traffic comparison seems to somewhat support that http://goo.gl/FdQi3 Swoopo started tanking when bigdeal started rising, but bigdeal hasn't been anywhere near as well trafficked as swoopo was in its prime.

I find it irrational that people got more worked up about Swoopo than they do about gambling/lottery business models. Unlike with gambling you are able to purchase a product before an auction ends and use all the credits you had used on it. It's a pretty transparent model provided you think it through. It's recreational consuming that leverages a host of psychological principles really well - love it or hate it.