I've seen a lot of remarks lately along the lines of "for regular people that the NSA isn't interested in..."
Those 'regular people' do not exist. The NSA is interested in everybody. Everybody.
Let me repeat that. The NSA is interested in EVERYBODY.
This should have become painfully obvious by now. The NSA collects absolutely everything about everybody, from everywhere. They don't care who it is about, as long as they get the data. They just store it for later usage.
"But," you say, "they don't have the capacity to read through all my uninteresting e-mails! Even if they have my data, it doesn't matter..."
'Big Data' is a thing. It is an entire industry revolving around the very idea of processing such giant amounts of information, efficiently. Even before 'Big Data' was all the hype, such tools already existed - just look at this video of Palantir for an example. Watching that video should scare the living shit out of you.
Hell, I'm working on an open-source application of this kind at this very moment. I can tell you with absolute confidence, that it is perfectly possible for the NSA to spit through the mountains of data that they have collected.
"But surely they wouldn't target me? I'm not an interesting person... even if they have my data and they can look through it... they wouldn't have a reason to do so, right?"
Even assuming that it doesn't matter whether this information might be intentionally abused in the future, manual targeting is only part of the process. A typical data processing solution will involve large amounts of automated analysis. To put that in different words, computer programs deciding who is a terrorist, a political activist, or some other 'undesirable'. And they make mistakes.
It's perfectly possible for you to be flagged as an 'undesirable', just because you fit some kind of obscure profile that you are not aware of. Even if you have absolutely nothing to do with what you are accused of being. It can make you end up on no-fly or harrassment lists. It can have any number of other problematic consequences. It's a secret trial where you don't get a right to defense, and aren't even informed that the trial has taken place.
The data collection of NSA and 'friends' affects us all. No matter where you live, no matter who you are, no matter what you are or are not involved in. The 'uninteresting person' is nothing more than a unicorn; a myth.