ProductWiki is, of course, a wiki for products. And while the idea itself ain't too shabby, I think it might have the same issue as YelloWikis - ie. a classic wiki isn't the right tool for the job. (I also wonder whether calling these sites wikis will alienate the 90% of people who have no idea what the word means, but I guess that's beside the point.) From the site:
We want to create a collaborative product information wiki. What the heck is that? Simply, it's a place where people (yes, real people) can share information about consumer products, their experiences with products, or anything else. The idea is that this wiki will, as time goes on, become more and more useful when you want to research a product before you buy, or get help with a particular problem that you have with a product, or want to take over the world!