A couple of people showed up at tea patry rallies with similar signs and were quickly surrounded so the press couldn't take their pictures and then claim that they represented the tea party.
It already is. If you take the picture in this article, and drag it to the google image search bar, it will tell you to drop the image, and then it will search for a face match. It finds dozens of places where this exact picture is posted.
In this case, the “visually similar” images don’t match well; I think if you did a crop for just her face, you might find her easier.
This works better though with exact picture matches, so it is good for taking people’s avatars and using them to find out where they really post to (many people use their facebook profile picture for their avatar in other areas).
What’s better is we’ll be able to go back over all the old pictures and ID the lying liberals.
The best reaction to these plants I’ve seen is when tea-partiers surround them with signs of their own (with arrows pointing to the offender) that say things like “Leftist Plant. Needs Shower of Rain,” “Liberal Stooge Showing Their Hate HERE!,” or “Community Divider At Work.”
Eventually, they leave on their own or are shown the door. But in the meantime, good clean fun at their expense!