Andy - left you a fuller reply to your points on the Zavvi thread, and I think it's less a case of the internet turning us into whiners, instead making us realise that we have something to moan about.
When one retailer answers emails within 24 hours, and deals with returns and refunds in speedy timeframe (I returned something to Amazon on Tuesday. The refund hit my account today), then it's almost impossible not to contrast that with firms that can't seem to manage anywhere near this. As has often been said on here, the true test of a retailer is how they react when stuff goes wrong, not when it goes right.
As for the emotional side of things, I think that is partly the consequence of the internet and electronic communication in general. We are used to swift communication via email. If you fire off an email and it disappears into the void for a week or more, it makes us feel powerless, and that breeds anger.
It's the electronic equivalent of being ignored by staff in a physical shop. Even an acknowledgement is nice and lets you know you have a relationship with that person or retailer.