D.C. police, frustrated that a teenage robbery suspect they have arrested kept getting released, took to cyberspace yesterday in an unusual effort to lobby judges and city officials to keep him off the streets. Exasperated by the third arrest of the same suspect in a string of 21 robberies, a D.C. police official sent an electronic bulletin to residents of Columbia Heights pleading for them to flood Peter Nickles, the city's top attorney, with calls and e-mails demanding that the suspect not be released. As of last night, he hadn't been. Under the subject line "ALERT ALERT ALERT ALERT ALERT,"...