SAN FRANCISCO — Q: How many apps are available in the iTunes store? Is it…

A. 100,000

B. 200,000

C. 300,000

D. 400,000

E. None of the above

The correct answer is E, none of the above, because there are more than 500,000 apps in iTunes — and counting. I share this factoid because for all intents and purposes a good number of the 500,000 applications are little more than potential bank killers.

Arguably, the greatest threat to banks today is not the new branch down the street, or ballooning marketing budgets, or throat-tightening regulatory compliance. No, the greatest threat are the multitude of apps that are surfacing. Apps — programs that accomplish various specific tasks or functions on mobile devices or tablets — are like tiny red ants that nibble at ankles of the megabanks. On some level, many of financial services startups are simply app builders.

“There has to be a consumer engagement within other platforms, like Facebook,” said Eric Connors, SVP of Products, Yodlee, at Bank Innovation 2012. “The question is, How can this approach be formed?”

Connors suggested that such engagement apps can be created by banks in many ways, only some of which are via private-labeled products. What types of apps can banks offer? Those that fit within the relative framework of the banking experience. One example of that might be tax preparation, which consumers preform in parallel to their banking activities.

“Why wouldn’t that be a part of my banking experience?” Connors asked. “Why can’t I manage my taxes there?”

Lest you pooh-pooh this apps “thing,” know that apps potentially might grow in significance, not diminish. Microsoft is now rumored to be considering an app platform — meaning the distribution of an API — for its core desktop platform. Now I’ve got your attention, right?