Flash mobs and flash gangs

Just as computer "hackers" became hijacked by conflation with criminal "crackers," it's quite unfortunate that "flash mobs" has become attached to these thuggish attacks. Until there started to be violent ones, "flash mobs" merely referred to (per Wikipedia) "a group of people who assemble suddenly in a public place, perform an unusual and sometimes seemingly pointless act for a brief time, then disperse, often for the purposes of entertainment and/or satire." (My emphasis added.) Something like "flash attacks" or "flash battles" would be more appropriate for these violent cases.

Here's a classic example of flash peaceful assembly (1st try using "embed video"):