Quick spam update: as you've probably noticed, the quantity of spam has been drastically reduced over the last week. We've installed a plugin that checks with a central blacklist to block registrations, and I figured I'd provide a couple numbers.
We've had the plugin installed for a couple hours shy of seven days, and in that week, there have been 138 "permitted" registrations, of which five actually went on to post spam. In that same time period, we've blocked 2493 attempted spam registrations, or one every four minutes.
Thanks for remaining vigilant and reporting the (thankfully much smaller quantity of) spam that still gets through.