Donor status on Fb sounds like a great idea for raising awareness and encouraging others to think and talk about organ donation (living and non). That said, during my process I talked to a number of professionals in the field and repeatedly got the same feedback: The sticker on your license (and likely the flag on your Fb profile) doesn't mean much in the end. If you've got living family, they'll be asked and their answer is going to hold weight. The most important thing you can do as someone who wants to be a donor is to make sure you're family is aware of your decision and willing to give the go ahead if that time comes.
Registrations like the one mentioned in the article seem like an awesome idea, but I'd still be interested to know how often they're contested by family. Bottom line is that there's probably no better plan than for your family to understand and be on board with your decision.