I apply a few drops of alcohol and it works again for a while. I was about to go to change it a few times, when it is really pissing me off, but then I would have to put sim card somewhere else, and this Android phone I have is kinda horrid, plus I will loose my contacts. I have an old iPhone 3G, but you can't sync iCloud contacts to it either. And then I have to pay for what I believe is a manufacturer's defect. So I am just slowly working through a bottle of alcohol.
I think that if the button is faulty it falls under warranty and you should be able to exchange it for a working iPhone 4 for no extra charge. If you have put alcohol in it, you have probably blown whatever warranty you had left.
I had a nasty experience with a 2007 Macbook Pro 3 years ago. One morning the screen didn't come on. Fortunately I was in the US at that time. I went to the nearest Apple store and discussed with them. Turned out the issue with the screen was a known issue. They fixed it the same day. No charge because it was a known hardware-problem.
They are generally quite friendly when you talk with them.