You're confusing two ideas. With Apple, the revenue model is always clear - even with the iPod - Steve Jobs just knew he could create something that people wou

You're confusing two ideas. With Apple, the revenue model is always clear - even with the iPod - Steve Jobs just knew he could create something that people would buy. He didn't launch the iPod and then worry about how he was going to make money off of it - it was always very clear to him - he was going to sell a ton of them. Tumblr still hasn't figured out a revenue model. They still have to fit that into their product. Being able to do so & do it successfully is integral to their product - otherwise it's just a cool tool that they're letting millions of people use for free. That was never the issue with Apple.