so if I was dealt a hand I have the liberty of seeing the mucked hand of any player that ended up at showdown - right ?
But where does it says that officially ?

First to show the hand - initial agressor on the river, then if no re-raises according to position clockwise (UTG, UTG+1...,button).
That's what i know.

Do a search here on 2p2 or google "IWTSTH" (which stands for "I want to see the hand")

It varies from room to room, and would be in the rooms rules.

In most vegas casinos, for example, the trend has been not to allow IWTSTH except for cases of suspected collusion.

Some rooms allow anyone dealt in the hand to invoke IWTSTH.
Some rooms only allow someone who also went to showdown to invoke IWTSTH.

Note that, regardless of the rules, its generally considered kind of douchey to do it.

pretty uncommon -- i know the Orleans does it that way

I would say that rule is common...the person who put in the last bet/raise on the river is the first to show and then travels clockwise. If there is no action, the person in earliest position is first to show.

What seems to be uncommon is how often this actually occurs. The player who thinks that they have the best hand is often the first to show - even if it is out of order. I think of it more of a courtesy to speed up the game though.

Personally, if in later position, I would try to encourage people in front to show. There is definately a plus in seeing hand ranges and how they act. With that said, I very very rarely invoke the IWTSTH (maybe 1 or 2 times in years) and let the action go its own course.

I think that you should tread very lightly if considering this. It is definately a controversial topic and could be very insulting to another player.

if you want people to not like you then you can ask to see their hand...

Seriously ... just don't invoke IWTSTH, because the games you're playing in don't have collusion, and even if they did, they wouldn't be good enough at it to profit. So just play poker and let someone fold if they want to.

This is a tough spot because you are allowed to see mucked cards of showdown hands but that is a pretty douchebag move.

From Robert's Rules:
Good discussion HERE