According to SearchEngineLand.com, “Google has discussed giving searchers the ability to remove domains from its search results.”
They attribute that from a discussion held by Hacker News user “bradly” asks who “asked Matt Cutts if Google would consider letting searchers remove domains from search results themselves. Cutts replies, “we’ve definitely discussed this,” and seems to hint that some kind of announcement may be on the way:”
Matt,Can you speak about the possibility for personal domain blacklists for Google accounts? I know giving users the option to remove sites from their own search results is talked about a lot in these HN threads. Is there any talk internally about implementing something like this?
[Matt's reply] We’ve definitely discussed this. Our policy in search quality is not to pre-announce things before they launch. If we offer an experiment along those lines, I’ll be among the first to show up here and let people know about it.
If Google were to allow users to blacklist domains it would obliviously hurt the value of the domain itself.
Google has its own list of blacklisted domains but it also has a method for getting the domain de-listed.
If users are allowed to blacklist a domain or groups of domains it would appear that those users would never see that URL again, thereby possibly greatly reducing the value of that particular domain.