"Survival of the fittest", you mean. There are plenty examples of big companies that failed (or would have failed wasn't it for government intervention).
The big aren't successful because they are big, they are big because they are successful.
Of course, you could argue that the incremental value of an added employee is positive for successful companies.
But there's an opportunity cost, if employees in companies are not developing, taking risks, and focused like they would be if they were working for themselves.