Apples and Oranges. Adobe is publicly traded. When (if) Facebook IPOs, they will not be worth $33 billion.
http://37signals.com/svn/posts/2585-facebook-is-not-worth-33...
http://37signals.com/svn/posts/2585-facebook-is-not-worth-33...
It's a bit like old school advertising (billboards, TV) versus Google pay-per-click ads. As soon as you can measure something accurately, it's value decreases.
Sort of like the maxim "Half my advertising works, I just don't know which half." Well, Google let you measure which half, and improve on the other.