I'm the trade mark attorney quoted in the article.

A lot of comments here are focusing on whether Airbnb can "own" BnB. That's not quite the issue. The interesting question is whether consumers would see "BNB" as indicating commercial origin, or simply as a descriptive abbreviation for bed and breakfast accommodation.

The fact that so many people in this thread immediately interpret it as the latter is one reason I described this as an uphill battle for Airbnb.