As an FYI, you can exclude specific domains from your Google results without using any special plugins. Tack the following onto the end of your search string:
-site:example.com
… where example.com is the domain you wish to exclude. There must be a space preceding the minus sign, but not following it; e.g., “my terms here -site:example.com”. You can exclude multiple domains by repeating the site flag; e.g., “my terms here -site:example1.com -site:example2.com -site:example3.com”.
(This also works in reverse, using a plus sign rather than a minus sign to require that results come from a specific domain, though obviously you can’t usefully specify multiple required domains. This can be useful for searching your own Tumblr blog if Tumblr’s goony built-in search tools aren’t cutting it, provided that your blog is visible to Google - just throw +site:yourname.tumblr.com in there.)