I bring wine only if I am sure it is not on the wine list. I always offer the owner and/or sommelier a taste. I'm not offended if the waiter pours, as that is what they are trained to do. For restaurants that we go to a lot, they tend to waive the corkage. Almost all waive the corkage if you buy a bottle.
A $10-20 corkage fee is totally fair. It is lost margin for the restaurant, covers cost of glass use, washing and breakage, and the small labor component of opening and serving. I also increase my tip amount to make up for the loss of the wine revenue - that's not the waiter's fault.
Some corkage fees are specifically designed to be putative/discouraging. I think The French Laundry charges $100 - but seriously, there's really nothing you could bring that wouldn't have an equal or better on their list.
There is a real movement to lower markups in the restaurants. I know of a couple that actually sell our wine for less than our retail price. They find they sell a lot more wine with a <2x markup. That being said, some of our other customers markup 4x. They make a lot more on my wine than we do!
There's a small movement up here in NorCal called the
Wine Patrol - fun read.