Disabling Third party cookies breaks some REcaptcha-using sites

We've had several anecdotal reports that our TBB default of disabling 3rd party cookies breaks REcaptcha on some sites.

It turns out there is a way to do REcaptcha without 3rd party cookies, but it is not the default mode. For example, drupal pre-6.x uses the 3rd-party cookie mechanism: http://drupal.org/node/1168740

So, do we give up? Do we enable third party cookies? I think so, but perhaps we can convince Mozilla to update the patch for legacy/trac#3246 (moved) for us first, so we can try it out.

If nothing happens on the Mozilla front, we should re-enable 3rd party cookies completely for TBB 2.2.x-stable and just rely on legacy/trac#523 (closed).