Visa is already the biggest credit card network in the world.Legendary investor Peter Lynch popularized the idea of "buying what you know." If you use and like a product or service, chances are that lots of other people do, too, and chances are that the company is performing well.Let's put financial powerhouse Visa (V -0.58%) to the test. Really, is there anyone you know who doesn't have a Visa credit or debit card? I'm sure people like that exist, but they're few and far between. Visa has nearly 4.5 billio ...