Obviously I have a different view on competitions or at least on attending them. I've been to nearly 60 competitions in the last 5 years and I can't remember a single one where I registered because of a time-limit. Of course, events can be a good argument (at least more or less uncommon events like feet or FMC mean) but I don't think that the complete removal of events happens that often.
But apart from that and back to the topic: if we had such a rule, what would be the penalty for changing the schedule too late? Who should be blamed?
And how can you find out who is responsible and distinguish between unforeseen circumstances and just failure?
I don't think this is possible at all.
I know of quite a few competitors that have a look at the time schedule and by estimating if they can manage the time limit or not, register for that event or better spend their time practicing for other events. This is especially the case at events like 5x5, 6x6, 7x7, 3 BLD etc. Events like these are also the ones where time limits get the most last-minute changes to win time.
As for breaking the rule (remember, my proposal didn't only mention a hard 'forbid'), what's the penalty for not providing a schedule, not having a score taker, not having a smoke-free venue, not having a competitors area, or for when the competition is not publically accessible? I think this is all the same category. We have those rules, but no penalty. The main purpose of the previous set of rules is to prevent unwanted situations and force organizers to organize an acceptable competition.
In the unlikely event that you have to make last-minute changes (I really think a delegate should have to quick-check and approve the schedule before a comp), the best option would in most cases be to let the competition run late. Like Hwee-Chong said: as an organizer you are responsible, so you have to pay up when you have to pay extra rent. If it's not possible to extend the competition and events have to be skipped, I'd highly doubt accepting another competition of that organizer and as a competitor I'd want part of my money back. Again: this can most certainly be prevented by proper planning!
@ Shelley: of course there are valid reasons. In that case you can change the schedule after consulting the delegate, after which the delegate would put the fire-drill, extreme weather etc. in their delegate report and everything is settled. Still, because you have some valid scenarios doesn't mean you shouldn't try to prohibit situations you actually can influence I think.
@ Bob: I'm sorry, but I don't see which unforseen circumstances took place. You knew who was competing right? So you could've adjusted the time schedule before the competition started. I understand a change had to be made, but I fail to see why you'd have to find out at the day of the competition. Unless I misunderstood and the change was made before the competition started (it's not entirely clear for me, reading your post)