I’m not sure how new this is (at least 8-days old), but I just spotted a list of most wished for items at Amazon – in the top right corner, where the Gold Box used to be – that is, "items that were recently added most often to Wish Lists". This will probably become more social as time goes by, for instance by letting you restrict it to your network of contacts and contacts of contacts (think Friendster meets Amazon Circles). Marketers will want to track how product desire spreads among people.
It would be interesting to compare what people fantasize about and what is actually purchased. It might be the case that some products are good at creating desire but for some reason don’t turn into sales success, for instance because of inadequate pricing or a bad reliability reputation. How long it takes to translate a wave of interest into desire then (purchasing) action would also be revealing.