I am not frustrated about nofollow's lack of immediate value at all. I don't personally care about spammed search results because I do very little business on the web and don't consult generic web search engines when I do anyway. My queries do not tend to include keywords that draw spam and the things I'm looking for are easily distinguished from spam.

But I care very much about spam on my web log, because it requires me to waste my time dealing with the excrement of reckless wankers. nofollow will never change that.

Hashcash is more reliable on web logs than email because all legit visitors will receive my hashcash implementation. No, it's not a perfect defense because some of them will not run it, but I can expect far more correspondents to send hashcash with their web log comments than with their email, and it's easy to design a fallback test that puts comments in a moderation queue. The effect is that only legit comments from people without an enabled Javascript interpreter and manually posted spam require my attention. That's a huge difference in wasted time I can have right here and now.

Oh, and it helps search engines, too.

Makeshifts last the longest.