It doesn't make them wrong but it does make them careless. If you build something on a weak foundation, knowing it will all come tumbling down sooner or later you'd better make sure beforehand where to go when the floor gets pulled from under you. With that I do not mean 'the Bahamas' but rather an alternative for the external dependency which can take over its role with as limited an impact for customers as possible. Doing so is not just good stewardship but it might also reveal new opportunities which otherwise would have been overlooked. By making things like Facebook optional you both reduce your own dependency on their antics as well as Facebook's power. The former is good for your own personal well-being, the latter is good for everyone else.