Why? Because he wants to reach an audience? He didn't say "If you want 5 bucks, could you vote for it on Hacker News?". If don't like it, don't vote for it.
The goal around here, AFAIK, isn't to get the most votes but to have a quality discussion. This guy is just begging you to get links to his site voted up, probably so he can get more eyeballs/ad revenue.
Some articles & videos speak for themselves. See http://ycombinator.com/newsguidelines.html .
What to Submit
On-Topic: Anything that good hackers would find interesting. That includes more than hacking and startups. If you had to reduce it to a sentence, the answer might be: anything that gratifies one's intellectual curiosity.