Left unattended, no accessory looks as menacing these days as a backpack.
At the airport. On the subway. At a sports event.
And, as a result of the two backpack-encased bombs that exploded near the finish line at the Boston Marathon, sports teams and leagues around the world are rethinking what kind of bags, satchels, purses and, yes, black nylon backpacks should be allowed inside stadiums and arenas.
The packs will even be the focal point of a conference this summer of stadium-security personnel in Orlando.
"After what happened … I wouldn't be surprised if the number of people eliminating backpacks would increase," said Lou Marciani, director of the National Center for Spectator Sports Safety and Security.
Next Saturday, more than 165,000 people are expected at Churchill Downs for the Kentucky Derby. Backpacks, duffel bags and large purses have been banned from the track since 2002 - part of the clampdown that followed the Sept. 11 attacks. Still, Derby officials have told fans their bags will undergo increased security checks for this year's race.
No matter where the world ends up on the bag-check spectrum, some fans may never again regard the pack slung across their body quite the same way.
"I never really thought about backpacks until last week, and now you notice backpacks all over the place," said Ryan Hershberger of Hartwell, Ga., as he headed into a Colorado Rockies game carrying a black backpack. "It makes you think."
Down the street, at the Denver Nuggets game, a handful of fans shared the same sentiment.
"I've been thinking about it all day," Joel Cross said on the concourse at the Pepsi Center in Denver. He and his wife traveled from Harrisburg, Neb., to attend Tuesday night's Nuggets playoff game. "We're from a community where our whole county only has 600 people in it. Nobody is going to bomb us because there's no one there. But we're coming to a populated area."
The NFL beefed up security for thousands of fans attending its annual draft, with metal detectors, pat-downs and about 20 percent more personnel in place than previous years. Backpacks are banned.