“What if your comment form also required the user to answer a simple question. The question could be something like ‘what is four plus eight’ or ‘what is the second letter of the english alphabet’.”

The problem becomes “what do you do about multi-lingual communities?” I personally have come across at least 2 weblogs that comment and post in english and one other language (I think german for one, swedish or norwegian for the other). How will you accomodate for them?

On DotanCohen.com I have both Hebrew and English pages. In Hebrew pages I have Hebrew spam-questions, and on English pages I have the question in English. Not difficult.

Would it be possible to distribute a centralised blacklist via BitTorrent or similar? Obviously still have the problem of innocent IPs getting onto it, but might resolve a few bandwidth and DDoS issues. Белая Церковь