Jessica’s Friday column “End of Tech Startups” argued that today’s big technology companies are nimble, smart, and well run—and that until there is another fundamental technology disruption, the window of opportunity for startups is limited to more traditional markets with less competitive players.

I agree with Jessica, but I don’t think she takes her argument far enough. This new generation of tech companies not only leverages technology to better compete, they also enjoy a position within enormous markets as marketplaces, and that makes them unassailable in a way that their historical brethren were not.

The upshot is, I believe startups are going to be locked out of certain types of businesses forever.