I am not a trademark lawyer, but I don't think there's anything with that. Companies trademark common words all the time, and it just means that no one else can sell that kind of product with that name, not that no one else can use that word.
Consider Tide, another P&G brand mentioned in the article. "Tide" is a common word, but P&G doesn't really own it—they just own the rights to use it for laundry detergent. I could start a company selling a completely unrelated product called Tide, and I think I would be legally in the clear (just so long as someone else didn't have a trademark in that area). So they can trademark WTF for a line of dish soap or whatever, and it just means that other companies can't ALSO sell a line of dish soap called WTF.
Edit: Cross-posted at the same time as Rivka.