On the other hand, it might be easy to beat Facebook -- they have 10 years momentum locking them in to a particular course. But the key is that you won't beat

On the other hand, it might be easy to beat Facebook -- they have 10 years momentum locking them in to a particular course. But the key is that you won't beat Facebook by building the exact same thing that Facebook is building. You have to build something more focused. You have to throw away all the cruft that they've built up over 10 years and identify the core value. There were impossible to beat spread sheets before Excel, impossible to beat word processor before Word, impossible to beat drawing programs before Illustrator (er... I don't know if that's actually the popular thing right now...) Those loosing applications were loosing customers well before feature parity in their rivals. That's really the secret in competing against the established competition: don't build the parts of their app that suck, and spend a lot more time perfecting the parts that are great than the behemoth can justify. Work with the rifle like precision of a team of 10, rather than the shotgun like vagueness of a team of 1000. Know what's important, what's not and concentrate on execution.