It's no surprise that Facebook is valued so much. Although, HN would loath this move but these ads don't feel intrusive at all. They are already making ~$2.5B in profit in a quarter and who knows, that could possibly be just scratching the surface. Facebook is smart enough to gradually up the amount of inventory without vexing its users.

Zuckerberg's genius was to realise that their primary objective is to create an engagement platform and gradually move towards monetisation; grand vision, or plain luck, it's working marvellously.