Growing up, my family always called LEGO toys "legos" as if an interlocking plastic building block was a "lego" and more than one would be "legos" (we didn't have the online communities to tell us we were wrong). Had I heard someone say to their child, "Go play with your LEGO," I would have felt really bad that they had only one. I was just that kind of kid -- guilty for what I had, but so unwilling to share my "legos".
Now that I'm older I can see the problem. If you tell someone to pick up some Kleenex or a Coke at the store, they may return with a different brand facial tissue and a different brand name cola. LEGO would rather not have the same thing happen to its building blocks. I get that and I'm sure my children would be disappointed if I were to buy them Mega B!#cks when they ask for LEGO.
And I also understand that this is going to be different from country to country, region to region, family to family. In the US, the cola example seems to work better in the south. In the first few months after moving north, my wife would get annoyed when she would ask for a "Coke" and someone would answer, "I'm sorry, we only carry Pepsi products."
But I don't think I'll ever be able to make LEGO sound right in my mind -- old dogs and all that.
Still, I'm very careful when talking to my children about LEGO toys. They know what's right. I may be a lost cause, but I won't raise backward children. And I have eurobricks.com and AMC's Mad Men to thank for that. Cheers all.