Cervaise’s answer is not accurate. There is a valild reason for sampling wine before you drink it. There are any number of things that could be wrong with it, cork taint being number one. And as already noted, the chance of the second or third bottle being corked is the same as the first (and depending on who you ask anywhere from 5-10%, the cork industry claiming lower numbers, winemakers and sommeliers claiming higher.)
You absolutey should not return a wine if you simply don’t like it. A sommelier at a finer restaurant will most likely forgive one such send back, maybe more (the customer is always right, even when he’s wrong), but you’d be pushing it.
Some common wine flaws:
TCA/Cork taint - If the wine smells like old books, wet cardboard, musty newspaper, it’s ‘corked.’ Send it back.
VA(Volatie Acidity)- Vinegar or fingernail polish remover smell, depending on severity. Rare, but it most certainly does happen.
Sulfide flaws - There are several kinds, with different smells, burnt match, cabbage, rotten eggs are the common ones.
Oxidized/Madeirized - Cervaise’s point might be true here, there may be less of these nowadays, but they still occur. If the wine is an off color, smells like sherry (oxidized) or madeira (madeirized, or stored at a high temp.)
Brettanomyces - Some wines, especially EU wines, contain more Brett than others and it is considered a good thing, but too much is considered a flaw - Sweat, horse blanket, barnyard smells.
There are probably a few more, that’s all I can think of off the top of my head.
I can’t say for certain if we’ve been offered tastings of a second bottle of the same wine while eating out. Maybe. We are most certainly offered a tasting in a new glass if we order a bottle of something different, which we sometimes do.
For the last 6 months or so I’m averaging tasting about 25 wines a week. There usually are at* least* 2 or 3 bottles out of 25 that are off in one way or another, and it’s rare that all are in perfect condition.
I’ve got an email out to a Master, I’ll let you know what he says.