I've never seriously thought about a sock club, at least not for more then 2 minutes. I do love making socks and have a bunch now. I also have more sock yarn then a person should ever admit to. And not every sock book ever published, but a good many of them, plus countless free sock patterns.
I'd worry I wouldn't love the color of the yarn, or would hate something about the pattern. they don't really seem to be a bargain to me, you know? I'd just rather buy the yarn I want when I see/want it/can afford it and find a pattern.