Centmail is a scheme which makes charity donations have a secondary value, as a stamp for email. When discussed on newscientist, slashdot, and others, some of the comments make the academic review process appear thoughtful :). Some prominent fallacies are:
- Costing money fallacy. Some commenters appear to believe the system charges money per email. Instead, the basic idea is that users get an extra benefit from donations to a charity and participation is strictly voluntary. The solution to this fallacy is simply reading the details.
- Single solution fallacy. Some commenters seem to think this is proposed as a complete solution to spam, and since not everyone will opt to participate, it won’t work. But a complete solution is not at all necessary or even possible given the flag-day problem. Deployed machine learning systems for fighting spam are great at taking advantage of a partial solution. The solution to this fallacy is learning about machine learning. In the current state of affairs, informed comment about spam fighting without knowing machine learning is difficult to imagine.
- Broken crypto fallacy. Some commenters seem to think that stamps can be reused arbitrarily on emails. This ignores the existence of strong hashes. The solution to this fallacy is simply checking the details and possibly learning about cryptographics hashes.
Dan Reeves made a very detailed FAQ trying to address all the failure modes seen in comments, and there is a bit more discussion at messy matters.
My personal opinion is that Centmail is an interesting idea that might work, avoids the failure modes of many other ideas, hasn’t failed yet, and hence is worth trying. It’s a better approach than my earlier thoughts on economic solutions to spam.
That FAQ is mostly from our paper, not me!
And just to quibble while I’m here (it was actually an anonymous reviewer of our paper who pointed this out): the flag day problem is a little more specific — we’re talking about a run-of-the-mill chicken-and-egg problem.
I believe it is a good idea, but it should be mentioned that Centmail is a Yahoo! Research project.