What's with that Bottle?

So last night we had an interesting situation. We ordered a bottle of Burgundy which was absolutely delicious ( we preceded that with a Chinon Rose - also worth a try) and then ordered another bottle of the same wine - a Chenas 2006.
The second bottle did not have the same quality of taste as the first and all four of us at the table agreed - the somelier then tasted it and said it was fine.
In a funny way it was - it didn't really deteriorate like a corked wine would after it's been opened - it just didn't have the yummyness of the first bottle and to be fair it was disappointing but drinkable.
This of course led to a discussion which brought up some questions about wine service, the most pertinent of which was:
Just because a customer doesn't like a wine, should the restaurant take it back and open a new or different wine?
I say yes in most circumstances as long as the customer is not taking advantage (hmm what does that mean?), although I think it's important for the customer to realize that this is a courtesy thing not a pre-requisite - when drinkers order a particular wine they are not tasting it it to see if they like it but to see if it's corked. Also maybe get them to taste it in a different glass (it could be the glass!).
Other things that came up in conversation were whether the modern diner likes to have her/his wine poured for them/the whole fad of wine doggy bags and over-pouring and upselling.