Mike Gunderloy knows how to get people to upgrade from the free version:
You know what I really want from my news aggregator? A filter I could turn on to simply destroy any incoming message on the merits of C# vs. VB or Hungarian naming. Perhaps one that would go out and actually delete the originating Web site could be a value-add for the Professional Edition.
Though I suppose it would probably need to set the Evil bit. (And you know there are already people delivering things with the MIME type “application/evil” – I’ve got at least one thing in mind myself.)