I never post on these types of heated discussions. But I have to this time.
Ok, TECHNICALLY, it does not lengthen anybody's wait time. However, it is slightly ANNOYING! Here's why I think it can be annoying:
Little Johnny rides with Mom. Dad is in line already..
Annoying scenario #1: Dad gets to the front of the line before Mom can hand off little Johnny b/c Johhny was soooo excited by the first ride that now he needs a potty break. Or something. So now others have to go around Daddy until he has possession of little Johnny. That's annoying to me (and probably to dad too!). Even though it does not technically lengthen anybody's ride time, it just is a little annoying.
Annoying scenario #2: Daddy is in a spot in line where little Johnny can't be easily lifted over the railing to Dad. So Mom has to physically walk through the line to get him to Daddy. Again, that is a little annoying. Not WRONG technically, just annoying.
I DONT get upset when kids need potty breaks and need to leave the line and get back into line again. Heck, I have kids and understand that when they have to go, THEY HAVE TO GO! However, I personally think families should try to wait together. I enjoy that time with my family. If we want to go on a ride twice, we all wait together twice. Life is tooooo hectic to be worrying about chucking bubba, jetting johnny, or whatever they call it. Slow down a little. If Johnny HAS to ride twice, do it again later.
P.S. I paid alot of $$ for my trip too!

We are park-commandos and have it down to a science to be able to ride most rides multiple times a day without these gimmicks. However, our only personal rule is wait as a family. No hand-offs! Its technically ok that others do it, as it usually doesnt REALLY affect anybody's wait time, its just annoying to me! Not much will seriously make me upset because I am at DISNEY WORLD. But I do find some things slightly annoying.