Strange, I have nothing but good things to say about SparkFun. I've had one problem with an order which they handled very elegantly. I have a feeling this is a isolated incident that they would handle through emails to them directly.
I will happily pay for a second shipment from another vendor rather than dealing with the possibility of a "wrong" part or a defective part.
I understand. But like many have said, it's probably just isolated instances (you just happen to be the unlucky one who gets the ace every time). One thing that I must give to them is their readiness to publish the eagle files for most, if not all, of their products (at least, the ones they designed themselves). Other companies tend to monopolize upon their products by keeping schematics to themselves (cough, cough - pololu) but sparkfun really stays as true as they can to the open source spirit.
I just thought that it was silly, even humorous, that some peevish clerk decided to teach me a lesson for improperly addressing, or labeling, the envelope in which I returned the part. They never bothered to open the envelope to see what was inside, and they knew that I was sending the part back.