I have used Askimet since its inception, and frankly it is not holding up to par. I have had some of my pro blogger colleagues convince me on the Growmap GASP plugin that Andy Bailey helped put together (same creator of CommentLuv) and they have had next to nil on spam.

Do not get me wrong, Askimet can be a lifesaver at times (as it has blocked over 200,000 spam on my own old site), but I think if Askimet is going to set a price... set it- do not let it be up to the user and perhaps have a moderation queue for people applying for the free account. It might be work, but it would certainly allow them to inform people whether they need to pay or not. As some of the people above have mentioned, it is important that Askimet draw out the guidelines on what constitutes as free.