A moat in business isn't a static thing that you build and then leave forever.
Apple's moat is its supply chain with Tim Cook built out.
Coke's moat is its bottler and distribution chain
Visa's moat is its ubiquity world wide
Google's moat is its search technology and infrastrucutre, both the 85,000 employee's it has and its data centers world wide that any of these engineers can harness.
None of these companies built that years go and then left it. These companies spend billions a year on updating their moat's. And if big companies can innovate, then their "moat's" are one area where they probably have an innovation advantage on competitors.
I'm with Buffet and Peter Theil on this one, give me a moat any day over a company that is continuously innovating trying to find a working business plan