A different kind of vigilante: If you're on the New York City subway, look out for the guy snapping photos over his crutches.
Courtesy of the Best Week Ever folks, I encourage you to enjoy a blog that goes by the name People Who Sit In The Disability Seats When I'm Standing On My Crutches. And it has the URL to match.
Philosophically, I have a lot of doubts about guerrilla blogs like this. As the writer points out himself, you can't always tell whether people have a disability themselves just by looking. At the same time... I can sort of understand how he became frustrated, and he's certainly right that a good number of these people are working hard not to see him.