Tumblr is a great example of a startup which follows the 'tribes' principle by Seth Godin. They came up with an idea, began with the product, and let the tribe

Tumblr is a great example of a startup which follows the 'tribes' principle by Seth Godin. They came up with an idea, began with the product, and let the tribe dictate where it goes next. It's expanded to much more than a overly simple blogging interface, now it's a full fledged blog app. V5 looks amazing and the video demo does it great justice.