You'd be surprised at all the consent forms I had to sign, as did my wife when I underwent the scalpel. It was actually scalpel-less, but I digress. One of the forms I signed was to acknowledge that I was going to be sterile, and that while reversible is successful in 40% of attempts (and costs $4k out of pocket, no insurance on that), reversal is not guaranteed and you cannot hold the doctors liable.
That all being said, that first numbing shot is a doozy, but the rest was more pain between my ears than anything else.