This is definitely a prank, and a good one at that. One of my funniest experiences in NYC was a guy with a bunch of goods for sale on a blanket near Union Square. One of them was a big dildo. I thought it would be the perfect way to end a relationship--use it on the partner you want to get rid of then when they say, "wow, where'd you get that thing?" just say "oh I bought it off some homeless guy on the street."