The salient point here is that the offending tweet was apparently made some weeks ago. This public act was done deliberately to send a warning signal that Big B

The salient point here is that the offending tweet was apparently made some weeks ago. This public act was done deliberately to send a warning signal that Big Brother is everywhere and sees everything. It might have caused some unpleasantness if they had made an example of Americans so they chose a foreign national. But then again it is just security theatre. They've made people aware they monitor Twitter and (EDIT I would guess) can mine it for historic comments so people will now take more care when using Twitter thus diminishing the value of the monitoring. This was a PR stunt for a purpose we may never understand.