I may never be able to ignore a street or subway poster again; I might not even feel I have to bring a book with me when I head for the train. It seems there's a current (and possibly snowballing) genre of street art which involves the alteration of commercial posters by making them into collages assembled from their own materials or paper cut from neighboring posters.
They're potentially so much more elegant than the Sharpie alterations we've been seeing on these boards for years, even if they have to sacrifice that form's occasional textual sophistication.
I spotted these examples and a number of others all near and inside the Morgan stop of the L train late Tuesday. The first image represents almost the complete framed poster as I found it, fully obscured or removed and converted into a rather delicate friendly greeting. The second two are details of separate works, but the third shows every square inch of a framed advertisement which has been converted into some serious political commentary.
This stuff can be quite beautiful, lots of fun or very provocative, and sometimes all at once. I called it "slash art" when I saw it this week, although this name probably plays into the hands of the police, who must already be pretty serious antagonists for these artists. "Cutups" or "cutup art" would seem to work too, but the form seems to have already acquired the moniker "mashup" while I wasn't paying attention.
More examples, from Poster Boy, here.