This. Can you imagine if the Government had access to our social media contacts? "Six degrees of separation" would suggest that half of NSC users may have connections to Khalid Masood, via Facebook or Twitter or other apps. Yes, of course you'd still be "innocent" (probably), but can you imagine...
Maybe someone else has mentioned that football fans in general were treated as scum by Thatcher's government, and there are/were a number of laws that pretty much only applied to football fans.