> I’ve always felt a bit guilty. That particular feeling in the gut when you owe something to someone.

So, firstly, everything this guy got was freely given. There was no expectation of reciprocation, so he doesn't owe anyone anything. That's part of the beauty of the internet gift economy.

But, i bet that he has given something back. Maybe not contributing content of his own. But has he ever voted up a post? Voted down a comment? Flagged something? Reported a bug? Enabled usage statistics reporting in some software? All of those are tiny, but non-zero, contributions to making the web better.