Could it be because time spent online is filled with upward/downward comparison ("I'm worse/better than people higher/lower on the social ladder", respectively), sensationalized apocalyptic news and people engaging in dishonest and malicious behavior a la 4chan?

Or, maybe, because of the fact that you're looking for a relief of a social kind, and when people don't message you when you most want them to, you feel even worse because now you feel about about yourself and seemingly have confirmation about the feeling? Add to that that people never post online about being sad — so you don't see that others feel the same, sometimes, and don't develop this reverse empathy — and you a cocktail of things that are going to kill you from the inside unless you quit soon enough.

I've had enough ramblings lately, and I have enough sanity left today to not jump into another one. Here's the thing I've noticed, though: in my experience, people seldom engage with each other meaningfully and positively over the Internet — and I would love to be proven wrong. It's because of this engagement that Hubski and certain subreddits stand out; I don't know if there are many other such places.