Higher purpose: The idea is this: a postpone "lock", to prevent someone from easily postponing a task day after day after day until that little "Postponed:" says "35 times". :) RTM makes it very easy to take an undesirable task and bump it off the list of things you need to do today. Unfortunately, if you're not disciplined enough, you can keep on bumping that thing down, and down, and down ...

Suggested UI implementation: a small opened-padlock symbol next to the "Postponed:" item displayed on the sidebar panel. (Alternatively, a lock next to the Postpone button.) When not selected, it could be a very light gray. When selected, it could be something dramatic, say, black on a red background.

Suggested action: Clicking the lock locks away the ability to postpone. From that point, clicking 'postpone' brings up an error message advising of the postpone lock. The user then is required to actually go and unlock things before he can go ahead and postpone it -- requiring more of a conscious decision-making process than just hitting 'p'.

Suggested added preference: set in preferences, the ability to auto-lock after a certain number of postponements, so that, say, after you've postponed something 5 (or 10 or 20 or whatever) times, you're prevented from postponing it further.