This is the last place grass clippings should be. Placing them on the street sets them on a fossil-fuel-powered journey that includes hauling, multiple turnings in windrows, then hauling again as fertilizer to a new location. Much better to let them stay on the lawn, where they quickly decompose and feed new grass growth. If one neighbor starts dumping them on the street, other neighbors can assume that's what's supposed to be done, and soon the whole block is violating an ordinance intended to prevent high-nitrogen yardwaste from polluting the nearby creek via storm sewers.
Sometimes, it's a misinformed landscape business that is first on the block to dump illegally.
County extension agents tend to recommend leaving grass clippings on the lawn, such as on this website for Mercer County, NJ. If you don't, you're lawn loses valuable nitrogen that must then be replaced by buying more fertilizer. The worst thing to do with grass clippings is to pile them up. The high nitrogen and lack of aeration favor anaerobic bacteria that raise a stink if the pile is disturbed.
