There are folks who argue that it is worth it to give up privacy for the sake of national security. These people will then insist that they have nothing to hide. But privacy is actually vital for the security of a democracy.
First of all, let's just admit that we all have secrets. I'm not married, so one of my secrets is that either I have had premarital sex or I'm a virgin in my thirties. Dennis Hastert had a secret as well. He spent a lot of money and may have broken the law trying to keep that secret under wraps. It's normal and understandable for elected officials to want to hide their past, even though the methods used aren't always legal or ethical. The kind of people who get elected to office often lead very interesting lives, then turn around and pretend that their lives are as bland as possible in order to cause the least offense to voters. Still, politicians should have the same right of privacy regarding their personal lives as any other citizen.
If the 9/11 attacks were carried out in a different manner, Dennis Hastert might very well have become President. And his blackmailer could have had influence over public policy. The personal secrets of powerful men can be used to control them, and by extension the rest of the country. So consider that there are thousands of private citizens who may get elected to Congress or the White House in the next 20 to 50 years. I don't know who will be President in 2032, but the NSA is likely gathering data on him or her right now. And that data could fall into the wrong hands. Whatever your opinion of Edward Snowden is, he is still yet another example of how the US government is very bad at protecting vital information. So one way to ensure a safer future is to not try to gather people's personal data into one big honeypot.