Don Norman explains why Words Matter: "Artisan? Customer? Consumer? User? Wrangler? Biot? Each of these words is a way to degrade the people for whom we design, a way of labeling them as objects instead of personifying them as real living, breathing people."
I've grown increasingly uncomfortable with the term "user" over the years - for me it seems impersonal, a means of categorising the audience for a service or product and separating them from the builders of the product. Maybe I'm oversensitive but I sometimes feel it invites a "them and us" mentality... in much the same way that I suspect "consumer" does for marketing folks. I think David Ogilvy said this much better, years ago: "The consumer isn't a moron; she is your wife. "