I recently discovered that google is indexing subdomains with "invalid" characters. E.g. -space- (%20) which makes the actual result in the serps inaccessible by direct click through with some browsers, e.g. firefox 1.5

Further more, this can be abused towards competitor websites when trying to gain seach traffic. I've written a bit deeper disclosure on my blog:
http://stefanjuhl.com/2006/how-to-steal-your-competitors-google-traffic/