I recently had a Google Custom Search box appear at the bottom of all the posts on my blog, which I don't remember asking for. After a bit of digging, I found that the Really Simple Share plugin was generating it. I'm guessing it's a new feature, that ReadyGraph have turned on by default in order to make some cash. Here's how to remove it:
Go to Really Simple Share -> Share Options.
In General Options, deselect Google Search Box.
And you're done!