...if they sell out of the item before they can process your order they really can't do much else for you.
Here's exactly what they did:
They gave you a full refund, a professionally written apology and notified of this in a reasonably quick time span (remember, this happened over the weekend and they likely didn't have staff around to pack/process orders).
It stinks that you got an order in and it didn't go through but I honestly don't see what they did wrong here.
Amazon, the biggest online store in the world, did the same thing to me last week. I bought a keyboard for my computer and it initially told me I would receive it in 2-3 days. The next day I found out that it was back ordered and it would be 2 weeks...point being, if Amazon can't get it right it's going to be a miracle for anybody else to.
I really am sorry that this didn't work out for you but I just don't think it warrants a boycott...just my opinion