Clearly the Delicious Search comes up with the most interesting results since they are a) hand groomed, b) recent, c) Del.icio.us is a new service and doesn’t have spam issues, and d) De.icio.us is very popular for sharing.. ummm… pointers to “liberated” content.
On the first page of the delicious search you find now only links to QuickTime rips of Pink Floyd at Live8, but also that four people have bookmarked the instructions to synchronize “Dark Side of the Moon” and the Wizard of Oz. Great stuff.
However, when you’re looking for a topic that is not as rich as Pink Floydsay the name of a friend, a company, a small storetagging starts to break down because most of the time you’ll get zero results. As time goes more stuff will be added to tags, but as that happens the Pink Floyd results will have a lot more results making it hard to sift through them. So, tagging has some issues, but the payoff of tag search is gonna be high.
Bottom line: Tag services like del.icio.us are amazing at times, but they are one of four of five search solutions that people will use to find what they are looking for. My feeling is people will use multiple methods for finding results on most searches, and tags are defiantly going to be one of the top two or three (standard search and blog search being the other two).