Thanks Rick, I have already voted for and am watching the issue since earlier this year. This would be a welcome enhancement to the user filter advanced settings.
From my comment in the "Spammers Using Self Registration" thread, I may have another idea to prevent spam accounts (copy & pasted from there):
The bogus account profiles are fairly easy to filter / suspend / delete as the country is random and our users are all within Canada. In the Location settings our Default country is therefore set to Canada. Considering this further it seems that on initial account signup page, JavaScript is used to automatically populate the Country profile field with the Default country. Extending this even further, the bogus accounts would seem to indicate that the bots are not JavaScript enabled. Could there be a browser JavaScript capability check done on the signup.php page before allowing any form data to be submitted? My idea is to have an additional setting in Site Administration > Plugins > Authentication > Email-based self-registration. I would like to see a checkbox for "Require JavaScript for Creating New Accounts" (default unchecked). Could the spam solution be so simple that it only requires the client to be JavaScript enabled? Might there be other mitigating factors such as accessibility, or any confusion caused by mobile or tablet themes?