Police adapt to the changes society brings because they are part of the social fabric. Woven into this fabric are brand new "threads" that are expanding the elasticity of our collective construct. Social networks are the latest in the human race's efforts to share, commiserate and help out when incidents/disasters occurs ... or when drama unfolds.
So trying to ban or circumscribe their use is futile at best, and most certainly misguided. It's as useless as a local sheriff trying to restrict the media's ability to show damages caused by wildfires such as was the case in Colorado last year.
So now, in an era where Twitter is a constant news feed for breaking events, trying to deny it's use is both senseless and counter-productive. People crowdsource the news. They are their own broadcasters.
Shutting them down or reporters tweets, is not the solution. This particularly applies when authorities are crowdsourcing a manhunt themselves.
So, you're asking the public's help ... through the media and then turn around and say: "oh well, you shouldn't tweet about this ..."?
This is what you end up with as a reaction: (from @CalFireNews)
#LAPD wants ##twitter turn off all # Dorner hastags replace with just a happy face :) #NothingToSeeHere #MoveAlongNow
It's perhaps a bit of an extreme reaction but that sense of ridicule was widely shared on Twitter and other social networks. It was in reaction to this: