Interesting, thanks for the links Zenobia.
I've wondered for a while why cookies, especially third-party cookies, seemed to be such an issue with Firefox. The MozillaZine thread about
Fx 2.0 / Cookies management makes the issue clear, as mud, which is really the root of the problem.
It appears to me that the main problem is disagreement between the Firefox developers as to what this option really does (in Fx 1.5), can do due to issues with iframes/redirects, and should do in future versions. This is made clear in these last few entries of this bug report relating to cookies.
https://bugzilla.mozilla.org/show_bug.cgi?id=349680#c13
To simplify this for those who aren't used to reading such things, it's really just stupid development bickering and mis-understanding. The ability to block third-party cookies is limited, so some feel it should be removed, while others think it should stay despite those limitations. By making it more difficult to find and use, they have simply made managing cookies even more difficult for their users.
The third-party cookie blocks in Internet Explorer and other browsers undoubtedly have some of these same limitations, but at least the most common ones can be blocked by the browser itself. This is the only really effective means to protect from such tracking cookies, since they are mostly used to track a users movement between sites during the current online session, so deleting them later has little value.
Completely blocking all cookies doesn't work well since this will often 'break' the access to some sites and not allow the experience that cookies offer for sites you might trust to use them. So the only truly effective system is to block all known third-party cookies and prompt the user for their decision on whether to allow or block all others, since this will catch all types of cookies no matter their origin. This can be a bit noisy, especially when browsing to new sites, but it does work.
Note that Internet Explorer 6 (and 7) allows you to block all third-party cookies and separately select to permanently allow/block each first-party cookie by site, so it won't prompt in the future but operates the way you have chosen. You can also browse the list of these decisions and remove/change them later if desired.
Removing the cookies later with Spybot S&D is obviously a possible solution, but to me it's just indicating that the cookies have already done their job, so the browser has failed to allow me to protect myself. This seems such a simple situation to fix that it makes me wonder what deeper issues exist within Firefox that haven't been resolved due to developer disagreement. This is also an obvious potential side effect of Open Source type devlopment, since there really isn't anyone 'at the top' to make such choices, good or bad, so they instead languish in a confused state of discord.
Bitman