[mlinsey]

Another example from the video is that a 10M valuation for a startup isn't really saying the startup is worth 10 million, but rather that it has a 1% chance of reaching 1 Billion.

One can actually look at Facebook the same way. One could argue that Facebook is competing with Google at being the primary way people discover information online, and at being a driver of incoming traffic. So one could say that Facebook's valuation with the GS investment reflects a belief that Facebook has around a 25% chance of becoming as valuable as Google.