Why is it baffling that people complain about getting banned? It is a total PIA for a reseller. I agree with you somewhat when I see people arguing that stores have no right to ban them or that the stores are stupid to turn down business, etc. But...the mere fact of being banned...totally understandable why someone would kvetch about that.
On the question of restraint, speaking as someone who places a lot of large orders, I do what the stores allow me to do until they don't allow me to do it anymore. These stores are not stupid. They all know that resellers are buying from them and they all know how to disrupt or prevent resellers from doing so. In my experience, most stores care far more about people who do certain things that cost them money (e.g., return & rebuy) than they do about people who simply order massive quantities of product. Those that don't generally implement measures to prevent it (e.g., LEGO Shop at Home and Barnes with their hard quantity limits).
I've been banned from a number of websites. It is annoying, but, at the end of the day, it's no real skin off my back...it just means I have to adapt my sourcing strategies. And stores don't make massive changes to their policies in response to a few resellers...they just ban those accounts. Stores make massive changes when the aggregate action of a large numbers of resellers causes some type of large-scale threat to their business like when Target banned all tax-exempt accounts following some fiasco with a clothing line that sold out in a minute because of resellers.
Try to figure out how they've targeted you (name, address, email, CC, or some combination) and then find a way around it. Unless you doing something that really pisses them off or you're dealing with certain retailers, it has been my experience that hard bans are relatively rare.