Unfortunately, attacks against CAPTCHAs aren't limited to sw bots:
http://www.technologyreview.com/blog/mimssbits/25594/
<snip from above>
"How Spammers Use Low-cost Labor to Solve CAPTCHAS
Workers in Russia, Southeast Asia, and China are paid a pittance to solve
millions of CAPTCHAS.
CHRISTOPHER MIMS 08/11/2010"
</snip>

ymmv,
C.G.

On Wed, Dec 15, 2010 at 3:27 PM, Lisa Kachold <lisakachold@obnosis.com>
wrote:
>
> On most of my production Drupal sites, I CANNOT even enable comments.
It's a sad day when one cannot have a login based access that is not hit by
SPAM bots?
>

--
Carlos Macedo Gomes
http://claimid.com/cmgomes