Foursquare's adoption of a game dynamic when it launched is a particularly clever implementation of a social hook.

I'm really interested in the intersection between reputation, identity, and knowledge.

New York's niche is content, and content is becoming more valuable. Just think about what is more valuable: MTV or the cable system that you use to get MTV? Howard Stern or the radio station you use to listen to him? Ultimately, technology becomes a commodity, and content - real, true branded content - becomes more valuable.

If you have an idea that you can't get out of your head, do a startup. Otherwise join a startup.

If you have a native monetization system where the atomic unit of content is the ad unit, that scales down all the way to a small screen experience. That's why Twitter is performing so well on mobile.

Customers are a great way to finance a business for many reasons. First, customer financing is typically non dilutive. They want something from you other than equity in your business. Customers also help you fit your product to the market. And customers will help debug and improve the quality of the product.

If you want to create something great and do it faster than the competition, you need to be action oriented.