If you do, how the heck do you handle all the extra cognitive burden of one finger (or at most, two thumb) typing on tiny keyboards? Programming languages have lots of punctuation which is typically only accessible via extra key presses which switch keyboards - another distraction. And then there's the 'L' or 'M' problem: whatever virtual key a particular keyboard image puts next to "delete" or "backspace" ends up causing significant number of mistaken previous-character-deletes. There's a lot of extra (maybe unconscious) cognition going on when using a phone's keyboard that prevents me from typing coherent thoughts, much less code that merely compiles.