> So why would I want to "like" something?

Because you're an average user who finds it convenient to press this one button?

As opposed to:

* firing up the mail client and whittling through your friends to mail only those who might be interested.

Or

* starting a blog/twitter/tumblr account and getting people to check it.

With "like", you hit one button, and people see your recommendation. And since it's mixed in with everyone else's recommendations, it's not annoying like bulk-spamming people with news links and more satisfying than setting up a blog no-one reads.

I think it's dumb myself. But I clearly see why people do it. Like many annoying features on Facebook: it shrewdly exploits social customs.