After last year's bombings, Boston Marathon organizers are tightening rules for anyone competing in the event, with an unanticipated crackdown on both signs and costumes. Under the new rules, runners in costume will not be allowed to wear bulky clothes or anything that covers their face, and signs wider than 11 inches will be prohibited for spectators. The measures also prohibit large bags, suitcases, and strollers from the athlete's village near the starting line, presumably with an eye to the duffel bags used in last year's bombing.

The new setup avoids some of the more extreme measures proposed in the wake of bombing, but the rules will still have some unexpected consequences, including a significantly harder path for so-called "bandits" who want to join in mid-race. Under the new setup, joining in mid-race won't just earn the anger of their fellow runners; they'll be aggressively ejected by marathon police.