The answer is often the first because the latter don't have it out for you.

I'm a nobody, and fiercely proud of it. And I pity the NSA employee who has to monitor my Internet usage, they're going to see an awful lot of Javadoc, programming blogs, websites about plane crashes (and I hope they read some AdmiralCloudberg on Medium for themselves), and websites about rocks and faultlines.

In reality, as mentioned by other commenters, I'm not anything they're interested in, at best I'm a datapoint that advertisers try to categorise into a demographic (male, 30 - 50, doesn't give a shit about cars, into tech).

And anyway, they're already doing it, but impersonally.

It's the person who is very personal that I'm not enthused about.

Definitely nobodies online. I don't think anything I've ever done or will do would put me in the interest radius of big agencies, government or private (outside of perhaps advertising and a few exceptions).

I have however, encountered death threats or obsessive/hostile behavior from people online who decided they have a beef with me for one reason or another. I'm much more inclined to be wary of some unstable individual having the means to find my identity (and therefore my location)- potentially using this to act on their emotions IRL.

Unless you're actively plotting to overthrow the government, commit violence against politicians or public property, or participate in major civil rights movements, you should be more worried about a random nobody funnelling all their built up hate and frustration into making your life miserable than a three letter agency, yes.

The difference is that the three letter agency has a budget, process and middle management so at the end of the day someone needs to justify why they're expending resources on making your life miserable whereas the random obsessive weirdo just needs to convince a bunch of other obsessive weirdos that you're a garbage person they can turn into their "lolcow" of the day/week/month/year.

The three letter agency is more likely to inconvenience you out of apathy than to actually try to destroy you intentionally. The random nobody is more likely to try to drive you into suicide for a thrill.

Absolutely more worried about the "nobodies". I'm boring to big scary organizations. But individuals have a wide potential for varying levels of instability and vengeance. Especially online.