One of the problem of having a blog with a Google PageRank higher than 3 is that you get flooded by a storm of spam. Be it comment spam or trackback spam it's a waste of server resources and, if not filtered, could fill your blog with tons of sex related links and more.
Last year Subtext included a integration with Akismet, the de-facto only spam blocking service available for free on the net. But last autumn I received more than 1000 spam trackback in one day and more than 30.000 on the same day in my Italian blog and Akismet was not able to block them. So I was forced to disable them, and since then I don't trust Akismet any more.
Waegis is a online spam blocking service, but unlike Akismet it's build entirely with .NET, which helps .NET to gain a few points in the general web development community.
Aegis, in Greek mythology, was the shield of Zeus, the King of Greek Gods... let's see if it will defend us from the attach of the trackback spam.
Just a last note: today the Alpha release has been announced, so it will take a few months before it become available for the general public.