i've been using defensio (http://defensio.com/ http://defensio.com/) for about a year and have had great success with it. over 11,000 spam comments with 9 fals

i've been using defensio (http://defensio.com/ http://defensio.com/) for about a year and have had great success with it. over 11,000 spam comments with 9 false positives, and no annoying captchas. comments flagged as spam by defensio require an email address to go into the database (if it wasn't spam it doesn't require an address and will just post to the site right away). the user is then emailed a link that they have to click on to make their comment show up, which then notifies defensio it was a false positive. eventually i grew tired of the email bouncebacks from the spam submissions, so i started caching the ips that submitted the spam and automatically blocked access to the entire site from the ip after a number of spammy comments queued up. the comment spammers just flood the site with spam very quickly, so their spam count exceeds that quota and they are forever blocked just as quickly.