I have to learn your language to find the kinds of things you're finding when you search. Everything has its own language; every topic, perspective, desire, state, need, or interaction contains its own vocabulary. Sometimes as a searcher you find yourself required to research a topic but you don't know the language; you have to learn the vocabulary. You can do that with tag sites because you can see what kinds of tags are grouped together; what tags seem to "hang together" in a folksonomy. Once you learn the language you can, again, take that information to larger data pools like Google and do more thorough searching. But larger data pools like Google are a difficult place to learn new vocabulary because of the huge amount of noise and irrelevance (see #3) that you can get in your searching.
So it isn't sloppy, or so individual that it isn't helpful... There are insights to be had from the tags. Excellent.