I haven't been quilting for long at all, but the washing or not issue is definitely a personal preference and every group believe in their reasons for washing or not. I don't think we'll ever get to agree on one way to do it, lol.
That being said, I have to say that although shrinkage and bleeding are good enough reasons to make me prewash, I mainly do it for sanitary reasons. Someone commented that blots come shrink-wrapped into the LQS, but that doesn't IMO mean that they don't contain chemicals from the manufacturing process, and also once the wrap is torn, and the bolt sits on the shelf, many people touch, unfold, fold, their hands may be clean, maybe dirty, who knows?I personally cannot stand the thought of spending all these hours touching unwashed fabric, but I suppose I am weird like that, because bed sheets come wrapped, but I prewash them before using them and everything else too.