I got a message in Google Webmaster Tools about "Googlebot found an extremely high number of URLs on your site" with a long list of example URLs.
For some of the pages listed, there was nothing to prevent them being indexed. However, for some of the URLs, I have "noindex, nofollow"
meta tags as follows:
<meta name="googlebot" content="noindex, follow" />
<meta name="bingbot" content="noindex, follow" />
<meta name="msnbot" content="noindex, follow" />
<meta name="slurp" content="noindex, follow" />
<meta name="teoma" content="noindex, follow" />
I have read that Google will sometimes index pages that you block in robots.txt if they find another link that points to the page, but supposedly they respect meta tags?