I went looking for a thread the other day and never did find it. Politics covers a lot, as does Bush and other generic tags. I wasn't going to hunt through 40+ pages. The other tags that appeared were mainly useless.
This has less to do with tags than the fact that the Google search sucks for finding anything specific.
The key difference is that google just indexes pages, and has no post-level search. So, searching for a general subject works ok, but searching for a specific thing a specific member said (or anything that drills down under page-level) really is hopeless right now.
We don't have a good search feature right now because the old software's way of doing things just won't work with the number of posts we have. A significant number of posts weren't in the old search index either because the database table holding the word matches was crashing due to size and load. So we are going to have to either spend some serious money on Google servers that can connect to our database or make our own search engine that scales using lucene (an open-source software for searching).
The bottom line is that keyword search over millions of posts is not an easy technical challenge, phpBB hadn't solved it either and large forums on phpBB had to hack at their search or disable it. So it's not going to be very easy for us to solve, and it's going to take us some time.