Think of it more as playing the odds. Yes Facebook will be surpassed one day, but we don't know when.
Odds of succeeding to make the next facebook 1/5000
Odds of succeeding in building recommendation system for something that currently has no recommendation system 1/2.
Thinking about both of these problems for a few days you can come up with tons of interesting angles and technical problems. Every once in a while a major player will be replaced one someone else, but every day someone else will have a sustainable business in a less competitive area.
Odds of succeeding to make the next facebook 1/5000 Odds of succeeding in building recommendation system for something that currently has no recommendation system 1/2.
Thinking about both of these problems for a few days you can come up with tons of interesting angles and technical problems. Every once in a while a major player will be replaced one someone else, but every day someone else will have a sustainable business in a less competitive area.