I wrote a little sitemap plugin for one of my sites a while back too. Like the rest, it was to see what happens. I haven't had any problems either, but everything in the sitemap was as "relavent" as I could manage.
Another thing, as BishopWeber pointed out, because of my internal linking structure, and some quality backlinks, a fair amount of my pages were already indexed.
Seems to me that if a page is worth Google's attention (ie, it's not spam), googlebot should have already found it, so a google sitemap isn't worth too much.
Furthermore, if said site is full of spam, and said site spams that spam in a site map of spam, maybe the problem isn't the map to all the spam, but all the spam spamming spam?
