Why is this even news? Facebook has been crawling links for ages every time you post on the site. The crawler is how the link you paste gets a title, description, and sometimes a thumbnail.
These days we've got a lot more people and they show up all across the board.
Clearly if this is on the homepage, it was voted there by your peers. This kind of knowledge is completely obvious to many of us, but not everyone is on your level. Cut 'em some slack.
> To my bemusement, not only was the friend I was messaging away, I also hadn't even sent the link; I pasted it into the chat window but forgot to hit enter.
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."