Well, I found one interesting use of wikiseek: Searching for spamlinks on Wikipedia. Check out
http://www.wikiseek.com/results.php?q=sex - of the 9 links on the first page at the time I did my search (the one on Wikipedia itself not counted), 7 seem to be outright spam (I'm now going through them, so they might have disappeared by the time you get to the page).
One thing I find a pity is that wikiseek seems to only search the English Wikipedia. It would be nicer to be able to search any languages, perhaps with 'all languages' as a default.