CNBC Interview Trujillo re: Cell Phone Industry & Regulation

A questioned was posed regarding the cell phone industry now dominated by two players regarding whether this should be a concern.

The question made me consider other industries today:

Mortgage Servicing (the lenders who collect are mortgage payments): two players Wells Fargo and Bank of America collect between 25 and 50% of all mortgage payments!

Retail: How large is too large Walmart?

Banking: How substantive should deposits, credit cards, and other banking services be concentrated in the hands of Bank of America, JP Morgan, and Citicorp?

I undoubtedly am failing to identify similar concentration in many other industries. Your thoughts?