Guys...I think a lot of this discussion really comes down to the definition of "line jumping", and I think a lot of that definition comes down to intent. If you enter the line as a family, or group with the intention of standing in that line until the ride is completed, and then find yourselves with a small child (or, in some cases an adult who simply had too much Iced Tea at lunch

) who has a "potty emergency" and needs to step out an rejoin their party. That is an "unplanned" event which you did not intend to occur. It happens.
However, if one person, who did not want to ride Splash Mountain allows her buddies to go, and then join her in line of Big Thundermountain RR once they have finished their ride....then, the intent to "line jump" was there all along, and is, most definitely breaking the rules, IMHO. However, most of the time people will not be inconvenienced at these rides by small children needing to go potty....they are simply too short or too scared to ride these rides.
Most of the potty breaks occur in line for IASWAF, Pooh, and Peter Pan. And, in that case, I do think people should try to be more understanding. Last Friday night, we took our dd to see "Curious George". The theatre was filled with families and children who behaved as children...they talked to the screen, they laughed at strange times (because laughing is fun), and more than once, we had to let people by to take their child to the potty during the show. I look at it like this....we go to a "G rated" film, I expect children to be children...these things hapen. If, I had gone to see "Firewall", I would be a little upset at a noisy theatre.
To me, WDW is the same way....if you're standing in line for Pooh, please be understanding of a mom carrying her little one out, and don't give her dirty looks as she comes back in...it's Pooh!!! If you're standing in line for Rockin' Roller Coaster, and a team of cheerleaders (or other groups...I don't mean to pick on Cheerleaders, here) tries to come from the back to the front...well....do what you need to do.
Beca