You say that, but multiple people with intent to commit a school shooting/bombing have been caught because they revealed their intentions online. Monitoring do

You say that, but multiple people with intent to commit a school shooting/bombing have been caught because they revealed their intentions online. Monitoring doesn't have to be done to catch the stereotypical "terrorist", but can also catch people with psychological issues that are disgruntled. Now, is it worth it and does it work? I don't know, but there is precedent for people to post their intentions online.