The mega trend that is ethical consumerism is built on the idea of low impact ethics. In essence, people want to do good things and feel good about themselves but in a way that has a low impact on their lives. Additionally, one of the other big barriers to action is the perception that individuals can't make a difference due to the scale of the problems involved.
Therefore, an easy way for people to contribute, without having to radically change their lifestyles, and in a way that allows them to feel part of something that has enough scale to make a difference, is for them to buy ethical goods.
People still get their products, plus the emotional bonus that comes from buying into ethical brands, and good things happen somewhere.
As with everything else, the interweb allows for the development of new models for this behaviour. My mate Rowan reminded me of one today: The Hunger Site. This allows you to donate food to the hungry by clicking, turning the ad revenues of your click into a 'free' donation from you. Lovely.
A twist on this idea uses the affiliate marketing relationships online to donate. Portals like GreaterGood and iGive let you buy from large and small online retailers [the smaller ones tend to give better affiliate fees] and then the affiliate kickback becomes the charitable donation, again at no cost to the consumer.
Not really cause related marketing or CSR, these intermediaries look at developing mechanisms that enable consumers to direct advertising spend into ethical areas, by leveraging the power of the internet as an aggregator of consumers that advertisers are looking to reach.