fat-finger problem
n. The tendency to make errors on a device where the keys or screen elements are too small. Also: fat-fingers problem, fat finger problem.

Example Citations:
Sizable erase and undo buttons at the bottom of the screen let you fix mistakes easily. Nevertheless, anyone who suffers from the so-called "fat-finger" problem or has stiff or arthritic hands should approach the game with an ounce of patience.
—Jill Duffy, "Trainyard Express (for iPhone)," PC Magazine, February 14, 2011

The most striking observation from testing the Fire is that everything is much too small on the screen, leading to frequent tap errors and accidental activation. You haven't seen the fat-finger problem in its full glory until you've watched users struggle to touch things on the Fire.
—Jakob Nielsen, "Kindle Fire Usability Findings," Jakob Nielsen's Alertbox, December 5, 2011

Earliest Citation:
I really need to get this fat finger problem checked by a doctor, or get a bigger keyboard for my laptop!
—Jim Oost, "Script to map share (sharename two words)," Windows IT Pro Forums, September 29, 2000

Here's an even earlier citation that uses the phrase in the context of nanotechnology:

Imagine a tiny robot, equipped with arms small enough to grab atoms one by one....

"There's a fundamental problem with that dream," Nobel laureate Smalley said. "I don't believe it's possible to get the fingers on those arms small enough to do the job."

Despite this so-called fat fingers problem, beguiling computer simulations of little atom-sized gears and other machinery are all over the Internet nowadays.
—Carl T. Hall, "Brave New Nano-World Lies Ahead," The San Francisco Chronicle, July 19, 1999

The similar phrase fat finger factor is even older:

This is what I call the fat finger factor — while editing any configuration file (no matter how benign your changes are), you might introduce a stray character or two that makes a key command or parameter unintelligible to the server.
—Jonathan Feldman, Sams Teach Yourself Network Troubleshooting in 24 Hours, Sams, December 16, 1998

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