Today, penny auctions were featured in the main stream media - MSNBC ran an article on this topic. The main idea behind the article was to discuss whether penny auctions are akin to gambling and lottery. There doesn't seem to be a definitive legal answer to this question.
More importantly, the article touched upon the important fact of the class action lawsuit against Quibids. This seems to be the first case against such a big penny auction and it should give a good legal status to penny auctions. However, the most important question is whether they can weed out the scams. Sites like Quibids are not scams i.e. they will certainly send you the product if you win. This cannot be said of all penny auctions. This is why it is all the more important to read up reviews, like on this blog.
On my blog, you can read several reviews, including Quibids Review, ScoreLuxe Review, BidRivals Review and BidFire Review. Hope these help you choose legitimate penny auctions.