Shepherd - 12:18 am on Jun 19, 2013 (gmt 0)
does your site return a 404 under other circumstances
yes, normal 404 returned for pages that do not exist.
Do you-- or can you-- add a meta "noindex" to pages of this kind?
Do not but could however this would require knowing how thin is too thin so to know which pages should have the no-index. (in reality this is something we already know, just making a point)