There are two views of politeness. One is that it's a kind of magical fairy-dust that you can add to whatever you do by using meaningless words like "please".
That might be OK for teaching toddlers, but it's rubbish.
Real politeness is caring about other people. "please" isn't meaningless, it's a contraction of "if you please", and it means that you're recognising that the person you're talking to might not want to do what you're asking, and that you're accepting that they might choose not do it.
Giving an order including the word "please" isn't polite, it's gibberish. Saying "please" isn't polite, unless you mean it.
Now the message you get if you go to http://www.legos.com/
"... We would sincerely like your help ... Please always refer to our products as LEGO bricks ..."
Is, as far as I can see, genuinely polite. They're not giving orders or making threats. They're pointing out what they call the stuff they make, and saying that they'd prefer it if their customers called it the same. There's nothing to suggest that they are unaware that Cory Doctorow or anybody else can call it whatever they like, but like other global companies these days, they prefer to call their product by the same name everywhere (Snickers, anyone?). Unlike Mars, they can't rename their product from "Legos" to "LEGO", because it was never Legos in the first place, it's just that Americans seem to be a bit confused. So they've made this polite request. Complaining about seems ridiculously touchy.
The problem here is not BoingBoing, it is the people who never got beyond toddler level, who don't know the difference between speaking politely and being polite, who say "please do not smoke here" when they mean "if you smoke here we'll send security guards to throw you out", who say "please do not copy this CD" when they mean "if you copy this CD we'll sue you for $100,000". They leave us in the position where we're not quite sure whether the Lego message is insufferable bossiness or a mild request.
On reflection, the motive might not even be marketing. It might just make their skin crawl to hear the word "legos". Mine does, a little, and I'm nothing to do with the company at all.