“If I were starting from scratch today, I’d built on Facebook, not the Web.”
That is a really interesting comment to make because it implies that there could be a further layer on top of the Web as we know it in the form of Facebook or some other similar service which becomes the Windows/Mac OS/Linux of the Web and on top of which developers can develop their applications for the benefit of the community that makes use of the platform service.
Facebook, for example, is massive and the addition of these various applications to the list of available applications on Facebook has proven to be a tremendous opportunity to explosive growth for developers of popular applications on Facebook. Just as you can run 3rd party applications on your Windows/Mac OS or Linux computer, you can run a variety of applications on Facebook and if you add the social nature of Facebook to the mix, social applications like the Hot or Not Hotlists are primed for success. The Hotlists apparently reached 1 million views per day in just 4.5 days on Facebook, hence Hong’s comment above.
Put another way, here is a platform with a specific context and and a ready market for relevant applications. Wow!