[maxerickson]

I figured https://news.ycombinator.com/item?id=22276586 made the context clear enough.

Ford doesn't worry about losing their brand. Lego does. So Ford regularly uses the brand as a noun itself, Lego Group asks people to not do that.

[detaro]

The only risk I can see is becoming a generic term for "construction bricks". I don't see how me calling my genuine Lego bricks Legos contribute to that.

[maxerickson]

It's how trademark law is written, use as a noun indicates it is becoming a generic term.