It is just not just the NSA. Governments the world over are racing to introduce legislation that allows to them to monitor and store every email, phone call and Instant Message, every web page visited, and every VoIP conversation made by every single one of their citizens.
The press has bandied parallels with George Orwell’s dystopian world ruled by an all-seeing Big Brother about a great deal. They are depressingly accurate.
Encryption provides a highly effective way to protect your internet behavior, communications, and data. The main problem with using encryption is that its use flags you up to organizations such as the NSA for closer scrutiny.
Details of the NSA’s data collection rules are here. What it boils down to is that the NSA examines data from US citizens, then discards it if it's found to be uninteresting. Encrypted data, on the other hand, is stored indefinitely until the NSA can decrypt it.