In reply to Pavel Karoukin.

There are lots of hashcash plugins, but I haven't seen any which force calculations upon the end-user beyond very basic JavaScript processing.

Thanks for pointing me in the direction of that site. I always assumed "hashcash" was just a funky name people gave for when they used JavaScript to shunt around variables for antispam purposes. I didn't realise it was directly related to forcing a calculation on the end-user like that.

Nice to know I wasn't the only one who came up with a crazy work creating anti-spam idea :) It nicely validates my concept. I was a little uneasy about implementing it since I hadn't heard of others doing the same.