The BIG downside to "captcha"-like technologies is that it limits access to those who can use image-oriented interfaces. That excludes the whole blind population, or those who use text-only browsers for other reasons. (That also means the US Government can't buy or use your methods, since they can't legally exclude a disabled population so cavalierly.) Before you dismiss that group out of whim, ask yourself if there is any other way to accomplish your goals.

For every perceived problem, there is a solution that is obvious, easy, and wrong.

--
[ e d @ h a l l e y . c c ]

In reply to Re^2: Image generation by halley
in thread Image generation by cosmicperl

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