I'm sure the mercy rule applies in many sports and games and such. In JKA ctf, for example, every one in a blue moon there's that seriously stacked pug where the leading team is like 10 caps ahead when the game isn't even 15 minutes in (out of 20). Usually it's a case by case, and if it's bad enough people will sometimes set an upper cap limit to avoid wasting time.
I'm starting to wonder how we might apply this to siege, although I know it's much more complicated. It'd obviously be on a map by map basis if we were to set any sort of standard. Any ideas on this? I mean, ask yourself this: if a team finishes hoth in 4 minutes, and it doesn't appear likely that the other team would be able to match it -- is there even a point to wasting the extra time out of everyone's day? Or do you think it's better to just play it through?
A further complication to control, would be the exploitation of such a mercy rule: ie, forcing a 20 minute hold on offense just so the defense doesn't get mad, but being pretty darned confident that your team will win on offense. Take that on for size -- do you think that's even avoidable? Maybe this topic is pointless on that note, but I'm just putting the idea out there.
Before you give your input, do note that I've seen both "guys let's just see this through, maybe we have a chance" and "ok that's super stacked, we're repugging *75% of players spec*". I've also seen teams giving themselves handicaps (or sometimes, spam or specjoin boosts) to compensate for unfavorable pugs. So it's really up to you, there's no right or wrong answer to this cuz we've heard them all already.
Also, I have another proposition: if a set of teams produces a damn fucking close pug (believe it or not, it happens!), then they should keep those teams and change to a different map. Any map, even a broken one like cargo or desert. Saves 20 minutes or so trying to capt and pick again, right? And it's not like Euro pugs where they keep the same teams for 3 maps regardless of the result.
That's always a nice thing to try for the sake of experiment, and it's fun to interpret the results.