Uncharitably, how it works is the author of this link doesn't want to scan all 2^32 hosts himself, so he's asking people for URL's to their windows servers so he can reach them directly. I can't imagine a scenario where I would submit a URL.

EDIT: again, yes, there are no doubt thousands of bots doing port scans for this. In the uncharitable reading, this 'service' is how the author beats them to the punch.