Ms. Barnidge: Thanks for all of your efforts to keep the site free from spam. However, my hunch is that in the end, you'll have to have some sort of quarantine on blogs (if not on actual comments) if you want to stop spam entirely. I hope I'm wrong.
Here's another idea: we rarely have legitimate posters who initiate more than two blogs per day. Perhaps there could be a limit on daily blogs - or at least blogs on Saturdays and Sundays, as that seems to be when most of the damage is done. At least that would cut down on the number of trash blogs you have to weed through to find the legitimate ones.
Also assume that there's no way to ID the perpetrator(s) by their the IP address, so as to facilitate blocking their traffic that way.