What makes web apps successful?

For all web entrepreneurs our there: Fred Wilson, partner at both Flatiron and Union Square, has shared the top 10 principles for successful web apps. Considering that he has been evaluating web companies for about 15 years now, should be interesting to hear his advice. You can see the full presentation below, but in a nutshell, here is his advice:

1. Speed is not only a feature -- it’s a requirement.
2. The application has to be useful instantaneously. Even if you are building a service which requires days of use before getting to the heart of its features, give the user something right away.
3. The service must have a personality, with a unique style.
4. Do one little thing very well. Less is more, specially at the beginning.
5. The service should have APIs so that others can add more value to your service.
6. Make your application personal -- allow users to personalize the service to themselves.
7. Make the URLs self explanatory so that they can be more easily discoverable.
8. Similarly to 7, make your service as discoverable as possible, both for SEO and social media.
9. Your application should be clean, and get users started fast.
10. Being playful is extremely important. If possible, make your application a game.