Even the reputable CSAs have bad years. Remember, you're not buying a bushel of vegetables per week - you're buying a share of a farm. The harvest comes in, and is divided up among the shares, and whatever that division is is what it is. As a shareholder, you're taking on the risk that folks who own farms take. And if it's a bountiful year, you benefit. I think a lot of folks get involved in CSAs without understanding what it is all about, and they're invariably disappointed if the weather give them a bad year.
Also, one consistent aspect I've noted with the three CSAs we looked into here is that they are all driven by social action: You're not just buying vegetables, but rather you're supporting something you consider valuable, specifically local, small-scale, farming. The ascendancy of corporate-owned factory farming has had a devastating impact on local farming. While there's nothing wrong with what corporate farms do, that doesn't mean that individuals cannot pay a little more to support local farming, because they value it, because they value the opportunities it provides for the local farmers themselves, for organic farming in general (at least with our CSA), etc.