Well, the cop is facing suspension over it....I'm sure only because of all the video and photographs floating around the Internet. I do find it humorous that the cop says he thought the people were "anarchists." WTF?
Still I have to agree with Keith that these twenty-something GROWN ASS ADULTS should have known better. We had an incident in downtown Madison after a huge blizzard where these asshole college kids rolled a huge snow boulder that was easily taller than a person and just left it in the middle of the street. Those fuckers should've been arrested, too. Thankfully nobody hit it with their car.
Cop's suspension:
D.C. 'Snowball' Officer Faces Suspension: Top News Stories at Officer.com
Giant snowball left in the street:
Giant Snowball in Madison, WI - CNN iReport
Edit: This is the earlier snowball fight in December that thepetek referenced above.