A perennial YA book group fave is Janet Tashjian's wonderful The Gospel According to Larry, about a teen who becomes a huge star by advocating anti-consumerism. One of Larry's big life rules is that he only allows himself to own 75 items. I know I could never do that. I own a thousand BOOKS!
But it looks like Larry's ideals have jumped off the page and into real life: How to Live with Just 100 Things, from Time Magazine. The article focuses a little more on simple living and decluttering than anticonsumerism, but we of the YA lit world know that Larry did it first.