Live feeding for snakes isn't (IMO) at all humane, and is actually very dangerous for the snake in question if the prey is large enough to fight back. Rats have killed large snakes that have been left alone with them, and a single rat bite is enough to cause a nasty infection in many cases.
For snakes that tend to be difficult feeders there are things you can do (ball pythons for example). Firstly if you're going to buy a snake (which I'm also opposed to) only buy captive bred animals that are already eating pre-killed food. If the animal hasn't imprinted on live food yet then you don't have to teach it to accept pre-killed prey to begin with.
If they're imprinted on live prey one can try scenting the (pre-killed) rat/mouse w/ the snakes natural prey (gerbils, frog, etc.), leaving the snake alone in total darkness for 24 hours w/ the prey, dangling it w/ tongs, using freshly killed prey, etc.
If they still won't accept food then you do have the option of force feeding a snake, but it's very stressful for the snake. I personally would use this option before I live fed, I would see it as a battle I would have to fight sooner or later, and sooner is better to me. Try www.anapsid.org
for more reputable reptile information.
I agree that many reptiles make totally unsuitable pets (see my avatar for a prime example). Iggy isn't abnormal in that his growth was stunted by improper care (he's about 2/3 normal size), he has burn scars over his body from improper environment, his kidneys are starting to fail rather young because his old owners used to feed him cat food, and he was dumped at animal control during breeding season because they weren't prepared to deal with an adult male iguana on a rampage. He is expensive, time consuming, and sometimes he's damn ungrateful.
That's pretty much the story with iguanas in captivity, yet they're still one of the most popular reptiles in the US (they're also the # 1 abandoned reptile in the US). Large constrictors, monitors, etc. have similar stories.
If people are going to keep/breed exotics there are a few species that I think are more appropriate (corn snakes, some species of gecko, a couple others) but I would prefer is people just stuck to rescue until the current population dies out.