I'm fairly certain the old captcha was in some way broken. Not that it was OCR'd, mind, but there must have been some kind of attack to render it useless. I'll see if I can figure out from the Apache logs what the rate of verification question failed attempts is - maybe that's made the bigger difference.
I tried activating the reCAPTCHA plugin for SMF, but it's broken
I'll keep checking for new releases. Although if it ain't broken (current captcha), maybe there's no need to fix it.
With the older Captchas, once the spammers get hold of the session ID they can have a field day doing whatever they like...
reCaptcha is really good (once you can get to to work)...
Spam is a real bane, considering the emails that I got (and do still sometimes get), are totally meaningless.
Another really big reason why I moved from SMF to IPB was because of the spam problem. Unfortunately it's inherent in Open Source Software and probably their main source of income. Think Akismet.
The main problem I have had with openSource CMS (Joomla) has been that you have to really keep a watch out for patches and security notices... If you don't patch your install within 12 hours then all sorts of bots and script kiddies try to take advantage...
AFAIK the SMF developers are pretty well organised and have a strong leadership...
BTW, I am really happy that they have kept 'imode', and it improved on it at the same time... (i.e.
http://www.avforums.co.za/index.php?imode ). The option to "Go to full version" is a nice edition to the software for viewing full posts with images.