To sum it up so far:
a) There's a genuine chance that you - or somebody else with a similar attitude - may individually or cumulatively unwittingly contribute to a problem.
b) By ignoring the request, your example may also be encouraging others whose device(s) may have a much higher chance of causing trouble. If they do cause a crash they take you with them. It won't be much consolation to be still insisting it's not your fault as you go down.
c) Refusing to comply is likely to make you look like a jerk to other passengers and to the cabin staff. This may well bring down some kind of public hassle or argument on yourself. This is after all how this thread started. A fellow passenger got cheesed off with the OP.
Here's a link to an aviation blog with some examples that show why these rules are put in place.
Incident examples
As Harry says, if you fly then it's smart to abide by the rules, even if you honestly believe your device is totally harmless. If you get into an argument with the flight crew and piss them off enough you may find that they can apply a range of sanctions including declining to take you on the next leg of your journey and up to getting the cops to meet you on landing.
Does anybody really think a few minutes e-reading is worth that? Isn't it just more polite and reasonable (as many have said here) to just switch the darned thing off when they ask?