I think that this comment nails it.

In the end, it doesn't matter whether it was a tip-off or it was picked up by some Government threat-monitoring software. The greater end result is the same: a chilling effect on speech. If you aren't careful about how you consider this event, your response is "I'd better be careful what I say."

Edit: I highly recommend Bruce Schneier's "Liars and Outliers", it is a masterful work about the social costs of security.