Behind the FTC’s probe into whether Google (NSDQ: GOOG) and Apple (NSDQ: AAPL) are violating antitrust laws by having overlapping directors is a simple question: How much do the two companies really compete?

SEE ALSO: FTC Looking At Apple, Google Boards In Possible Antitrust Case

Philip Elmer-DeWitt at CNNMoney.com counts 10 areas in which the two companies have dueling offerings:

—Smartphone operating systems: iPhone vs. Android
—Web browsers: Safari vs. Chrome
—Music and video: iTunes vs. YouTube
—Cloud computing: MobileMe vs. iGoogle
—E-mail services: Mail vs. Gmail
—Address lists: Address Book vs. Contacts
—Calendars: iCal vs. Google Calendar
—Chat: iChat vs. Google Talk
—Photos: iPhoto vs. Picasa
—File storage: iDisk vs. Google Docs

We’ll add one more loose category, word processing, where Apple has iWork and Google has Docs. And with Android expected to arrive on netbooks later this year, the two companies will also likely soon compete in one additional (and major) area: computer operating systems.

Still, it’s hard not to run down Elmer-DeWitt’s list and think that the FTC might have a hard case to make. U.S. Antitrust law states that it’s okay for directors to serve on the boards of competing companies if the “competitive sales” of either corporation are less than two percent of the company’s total sales.

None of the markets on that list appear to generate more than two percent of sales at both companies, including smartphone operating systems, considering that Google gives Android away for free.

What do you think—does the FTC have a decent case?