What's up with the floppy (is it?) in the spokes of the rear wheel on the bike on the right? Is that some new trend or is that a unique feature of that particular bike? 'Cause just tonight (Sunday) I saw someone walk a bike (either fixie or SS, don't remember) with a thingie like that in the rear wheel around Chinatown.

Edit: I see, two of them are like that in the picture. What's up with that anyhow?