That's exactly what's been happening in the Fresno (CA) area. Once a law enforcement agency announces the time and location of a checkpoint, messages are posted on Twitter warning motorists in the area.
Law enforcement agencies and prosecutors are up in arms about the use of social media to warn motorists of checkpoints. But, as Fresno criminal defense attorney Brian Andritch points out, the purpose of publicizing the locations of checkpoints is to discourage people from getting behind the wheel after drinking. Whether checkpoints result in more arrests or not is immaterial. Should news of a checkpoint deter one motorist from driving after drinking too much, then the streets are safer.
If you want to increase your arrest numbers, just saturate areas in which there are a concentration of bars and restaurants and pull people over for not signaling lane changes after 2:00 a.m.
And, if you want to find out where those checkpoints are on your own -- well, there's an app for that, too.