The NeoSmart files has a brief commentary on the feasability of encoding schemes like PHPEnkoder.
First, he mentions that
What’s so special about that? Well, we can build a tower as high as we like. We can make it arbitrarily computationally intensive to decode the e-mail. Half a second? Easy, give it forty or fifty encodings. Five seconds? Sure. These “computational micropayments” can be worthwhile for a user to pay, but a spammer? Decode one, sure. Decode fifty? That’s nearly five minutes to get fifty e-mail addresses. How many of those people really need a bigger penis?
I don’t much like that future, though. Even if it’s a link a user can click to wait a minute for the e-mail address, that’s not ideal. NeoSmart is right, much of the problem can and should be solved server side. The only client side solution that will ever work will require human language: posting e-mail addresses as puns, jokes, tricks, songs. The only way to escape our symbol-processing machines is to abuse symbols: I’m Mike, and I hang out with hatted weasels! My plugin, PHPEnkoder, also spends a lot of time at the weasels’ place.
But I haven’t seemed to need either of those solutions, as I still haven’t received any spam at the addresses I’ve posted here — encoded, of course.