Years ago I used to collect wine and have bought and sold many, many cases. Hence it is unusual for me to pay premium process for fine wines in restaurants as I don't perceive the value in the mark up. Personally I rarely taste wine when offered in a restaurant, but I always release the bouquet and smell it. A wine that is off is immediately obvious in most cases. Bear in mind that I generally know what to expect as I tend to order wines I already know in restaurants and my tastes have narrowed over the years, hence few surprises.
Corked wines used to be much more common: defective cork letting the wine oxidise, poor storage, whatever. But modern production and bottling techniques, synthetic corks and screw caps etc all help, as does our tendency as consumers to drink much younger wines and these things have drastically reduced wines that are off or corked.
In 30 years of buying wines in restaurants I have only ever sent back four corked bottles. Two of them were LaTour on the same day where I expect the whole case was ruined. In all cases the sommelier also tasted and agreed. In fact with the LaTour he said "oh no" when he opened the second bottle and we agreed that maybe it would be a good idea to switch to my second choice, a Palmer.
I have had a few examples as a guest where wine has been accepted by the host but would have been questioned by me. I just kept quite and didn't drink it. Incidentally, I never actually sent wine back. I just ask the sommelier for his or her opinion. Discreetly. This always works.
Trained sommeliers know what they are doing and never make a fuss if the customer keeps it low key. These days, in the trade, as a proprietor, you do get a bit of prattish behaviour from a very few customers, and these are usually the ones who think they are tasting wine to see if they like it, or wanting to show off to fellow diners. Some restaurants allegedly have special techniques for dealing with such people.
These days in restaurants I tend to order off the lower end of the list, usually a youngish Rioja. In countless bottles I have never had one corked.