I remember a lot of riots. 1967, Watts rights (multiple), MLK Assasination, Rodney King, OJ, and WTO to name a few.
Normally these affairs were limited to a fairly localized area. During the Rodney King riots the rioters used the freeway system to move the violence out of the South Central area to other parts of LA. This was considered an inovation in riots.
. The Mexican Maffia has about 40,000 members in LA. If they were for some reason to employ these "Flash Mob" techniques, I forsee a major disaster.
Consider also the fact that several gangs have chapters all across the US, using this technology they could cause major disruptions in every major city and many minor towns at the same time. This type activity would quickly overwhelm the local civil authority and the National Guard.
Makes me thankful that I have retired to my remote mountain home.