Two Google Webmaster Help threads have complaints from webmasters and SEOs that the fetch as Googlebot feature in Webmaster Tools is not working.

Specifically, people are running it and are being returned a 404 error that reads:

Google’s JohnMu chimed in over the weekend to say he will send it up the chain to be fixed. He said:

Thanks for your report. I’ll pass it on to the team to review and get back to this thread once I know more.

I personally tried it a couple times and it worked for me but it might be a sporadic issue.

Forum discussion at Google Webmaster Help.