Yes that would be good. They could then look at the number of people blocking certain domains and de-weight them in the global results. Traditionally google seem against human powered editing (as this would be), but I think as the black hat SEOs run rings around them, its needed badly .
This would only work if 1) it was sufficiently painful to put in a block for your searches and 2) this had no effect on global results. 1) - It doesn't have to be extremely painful, just painful enough, such that true loathing is needed as motivation. This way, we filter out frivolous decisions. A few seconds pause would be enough. 2) - We need to let the reduced ad revenue do the job for us through the market. Anyth…
Re 1, painful? WTF? The whole point is to make it quick and usable. I can already blacklist sites the painful way, by adding them to a Google Custom Search page. The whole point is I'd like a quick add-to-killfile button, like email clients have had for decades.