1) Obviously the people they were spying on are not open about it. It might not eliminate dissent but it sure can limit it.

2) If the NSA can just get you to willingly post all your information in public out of fear of blackmail by the government I'm pretty sure they just won. Their goal is systems intelligence.

3) If I'm like oh look Mr. Jones, your file says you watch x, y, and z porn. I'm going to for sure start wondering what else they know.

4) My friends knowing and the public knowing are very different.