In mid April, Google released a new way to remove content from Google. Since then, people have been using it but there has been a lot of confusion on how it works and doesn't work.
A Google Group thread has dozens of posts with questions on why pages they remove, still appear. Or why it may take so long to remove a page.
Due to that, Susan Moskwa, of Google Webmaster Central, promised clearer instructions on the Google URL removal tool and also provided more details on what you should do to remove content from Google's index.
I'm sorry that you've been frustrated by the URL removal process! Just to clarify, here's what's required in order to get a URL successfully removed:
If you want to remove an individual file (a web page, an image, etc.), you can do any one of the following:
-Make sure that the URL returns an HTTP 404 or 410 status code
-Block the URL using a meta noindex tag
-Block the URL using a robots.txt file
However, if you want to remove an entire directory (or an entire website), you have to block that content using a robots.txt file. Just returning a 404 isn't enough; this is because it's possible for a directory to return a 404 status code, but still serve out files underneath it. Robotting out the entire directory ensures that all of its children are disallowed as well.
Forum discussion at Google Group.