I think one of the bigger challenge is that when you become bigger you launch more projects to handle the scale and each of those projects introduce new bugs fo

I think one of the bigger challenge is that when you become bigger you launch more projects to handle the scale and each of those projects introduce new bugs for which you need new team of engineers. Basically, once you hit scaling I think you end up with a super small team that managed to keep simple (instagram for example) or you end up with a huge team that explodes in complexity and needs to grow exponentially to handle all the extra complexity. Uber is very obviously in the later bucket.