Being first might be very lucrative. I might remember wrong here, but instapaper was an iOS only experience (with a kindle addon), and they are still rocking on, and the founder cashed out a long time ago. Every browser seem to have an instapaper built in nowadays, Mozilla even bought a competitior (formerly read it later now pocket?)

So yeah, buildin inside someone's moat might give you a cap on how big you will be able to become and will make you a tenant, but it could still be worth your while.