In the world on Blogs, it is likely that people will want to auto-ping their posts.
This means the post is immediately made publicly available to some form of a blog directory. This directory is mainly for machines to look at, but it is also available to end users.
Especially, a blog post X that person mentions on his blog Y generates two links:
The Ping feature will support all the possible pinging capabilities:
All of these Ping features must be performed in the background since pinging another website may take a long time (and if it fails, it can report the problem(s) to the author at a later time anyway.)
Pings that go out or come in need both to be checked with the Spam module. This is important because a large number of pings are just spam (i.e. from websites that are just trying to steal your juice and do not add any value to your posts.) This check should know whether a website has value and thus whether the pings need moderation or not.