Whether useful or not, or evil or not, Facebook is a technically solid platform and they have created an ecosystem around its content. Its far far more advanced than MySpace (which I believe was some sort of band-aid using ColdFusion), its like Google compared to Yahoo.
The sophistication of Facebook I see whenever I buy ads on the site...I can pinpoint ads to a narrow user-base, and this will be more on the spot than Google AdWords/AdSense.
Facebook is a decent platform for a group discussion or following a specific topic and so on. I agree 99% of the content is someone's children's stupid photos.
And Facebook is needed to counter Google. Else Google will be the only evil corporation, you need more evil corporations battling each other so that they will leave the proletariat in peace.
Will Facebook die? Probably not as its useful. But it may not be worth the crazy valuations and inflated stock prices.