My experience matches many of the others here.
I responded to an ad on Craigslist for a washer/dryer at a great price. I got a reply from Katy Taylor saying it was sold, but she gets them all the time from bidcactus.
I also wondered why someone on Craigslist would give away the site, but figured it couldn't hurt to look at it. However, it looks like you have to register to see what's up for auction - this seems like a strange for a legitimate auction to attract bidders. I found this site when I looked for reviews for bidcactus.com before registering.
After reading other reviews, I will not register (and certainly won't give them any financial information).