Is Facebook Like Google, or More Like Yahoo?

Here’s a very familiar story that we all know: A pair of college kids launch a directory of the Internet that grows to become the most visited site on the web and makes them very rich.

Then a few years later, another pair of college kids start a search engine, laser focused on one goal: to become the only search engine anyone uses.

That upstart search engine ends up blowing past the first company while they were off...