There's the daily grind of ignoring the obvious affiliate link begging emails. I have a well developed bullshit detector from being on the web since 1996. As it appears, I still wasn't skeptical enough.
I get this email written by an old lady explaining how my site brought her grand daughter tremendous joy. It was very well written, and felt very genuine. It had a "realness" to it as it had such an informal style and it clearly wasn't generated as it had detailed, human-selected specifics about my site.
Anyway, the request was to have a look at this other site she found. I opened it. It looked OK. Relevant for the field, no obvious visual scam signs, just pretty shallow content.
I figured to not do anything. I figured it to just not be that interesting, it still took several days for me to let it sink in that it was another link/scam attempt.
I guess I still had some humanity left in me that could be exploited. That is the point I'm getting at: the human damage of all this hostility. You're under constant attack without relief, and can only manage the problem by becoming a monster yourself. Somebody so cynical that they assume every interaction is hostile.
And there's the daily cleaning of spammers joining the site. As small site owner, you can't take a break. There's no such things as weekends. It's non-stop. They're not bots, they're people in click farms so there's no mechanism to prevent them from joining.
There's the non-stop hack attempts as is evident from web server logs. And the occasional ransomware email.
Mind you, I'm talking about a completely non-commercial hobby project. The threat level for even just that is completely disproportional. You're trying to run this small genuine thing yet the world aims to destroy it, every hour of every day.
Now scale that up to a large site, or imagine being a Facebook moderator.