Here's how I see this. For the average person, if an actual NSA person was paid to follow them or look at them, the NSA would get tied up and bored to death. There are far too many people using Sim cards than there are government employees.
So second, could this private information be used by a rogue NSA employee, say an old college boyfriend to stalk or "peep" into private correspondence? Snowden has absolutely demonstrated that risk, that any of us could be somewhat randomly spied on. But the odds of any single one of us being examined is still as low as previously stated. Annoying but low actual risk.
Could a dictator use this access to information to cow us into subservience? Seems a stretch. In the USA example, if a Democratic/Republican president let slip they were using this info collected by the NSA for political means, the opposing party would hang them with it.
So the most likely use is, as NSA claims, to catch bad guys. Saw John Doe used porn, saw Jane Doe was in AA, but no time or interest in that, they are looking for Bin Laden.
The second most likely use would be a politically active person trying to change the status quo. Like Martin Luther King. If FBI Director J.Edgar Hoover had his hands on this kind of access, the USA would have been screwed. But then again, they assassinated King, and today it would be much harder to cover that up. The FBI directors now have to worry about a Snowden in their midsts, which should keep them more honest.
Mathematically, I'm extremely unlikely to be affected by Bin Laden... the mathematical of terrorist threats is smaller than getting hit by a car (for now). And the likelihood I'd be targeted by a college stalker or NSA agent is also very small. So is the risk that my social security number will be picked off of dropbox. The risk here is that a true intellectual agent of change will be targeted, or that Al Quaeda or ISIS will screw the international banking system so bad that the entire world economy is screwed up and people panic and break into stores and start killing each other. So I sleep at night hoping NSA is as concerned about the latter as much as I am, and hope to God they also fear and realize the precedent set by J. Edgar Hoover.
In the final analysis, I hope people with liberal arts degrees choose to go work for the NSA. The one former employee of NSA that I know personally had a liberal arts degree, and I hope she's not alone. I hope people who care about and worry about the things I worry about are working there, and sometimes I fear the reaction to the NSA is similar to the reaction of hippies in the 60s to business and capitalism... all the agents of conscience were afraid to get their consciences dirty, refused to go into business management, and we had 2-3 decades of business management dominated by assholes. We want more Snowdens in the NSA, and hyperbolizing the agency's "evil" is perhaps the greatest risk.