Regardless of the way we would like people to use words, they will use them as they see fit. In the United States, most people are in a hurry to say what they want, and will shorten to the bare minimum to get there faster. This is why terms like "iced cream", "skimmed milk" and "creamed cheese" have been shortened, even officially, to "ice cream" (which never made sense to me as a child - there's no ice in it!), "skim milk" and "cream cheese". No one here would bother for long saying "Lego bricks"; I've never heard anyone say that, only "Legos". The LEGO Group is very aggressive in protecting their LEGO name. They own both lego.com and legos.com, although the latter will get you redirected to the former. They do not consider LEGO a noun at all; to them it is to be used only as an adjective. I think most Americans would be surprised to hear there is anything wrong with saying "Legos". I'm not defending or endorsing it, just reporting "the way it is", like tsuwm said. :0)