WJLA ran a piece last night on a sudden spike in shoplifting in the Dupont Circle neighborhood, citing a 70 percent increase in just the last month. That’s a pretty shocking number, and reporter Stephen Tschida lays the blame mostly on the same sort of large groups of teens who have been caught on tape recently at Logan area stores like Rue 14 and Universal Gear. Small retail operators have little defense against a large group of determined young thieves apart from installing seriously expensive theft-deterrent systems, something most small businesses likely can’t afford.