It’s cool to see a Web site reach a tipping point.

A few years ago, I stumbled upon MyFitnessPal.com. I try to track my calories and nutrition overall and I was looking for something to help me do that. The web site was “OK and not great”.  I stopped using it after a few days. It was a pain to search for food items and a bit tedious to remember what I ate that day when I got to my computer.

Years later, I downloaded the free iPhone app this past summer. I now use it every day. It’s a gorgeous app and simple to use. Most important, I can scan the bar codes on food packages to quickly track what I’ve eaten, on the spot.

The experience made me realize that some web properties have reached a tipping point. The mobile app is no longer an extension of the web site. The opposite is true. The mobile app is the core value proposition, and the Web site has now become a second-class citizen.

Personally, I think we’re just at the beginning of another wave in mobile, one that is focused on “mass customization,” a key investment theme of ours. We’re now in a networked world where the mobile user can customize an app according to his/her particular use cases and needs. This has all sorts of implications for targeting, advertising and development.

It’s exciting.