Product tagging becomes really popular now, here are examples how largest retailers / sites are using Tag Clouds:
... Amazon.com
... news.com.com
... ZDNet
... Netscape
... flickr.com
... Technorati
... Amazon Blog
... Technology Evangelist
... MSDN Channel9
And literally thousands of other sites!
Del.icio.us, Digg, Technorati, Furl, Google Bookmarks, Reddit, YahooMyWeb, NewsVine, De.lirio.us, Blinkbits, Blogmarks, Connotea, Fark etc. What is Social Bookmarking and how it can be useful for your online store? Let's try to find out.