the practical, legal effect of the patent grant, which patent legal experts tend to agree would’ve had no practical effect

I know it's not the main focus of this discussion, but let's just set the record straight. “Patent experts” agree on no such thing; it's just that one person's blog post has been quoted by multiple other outlets. That doesn't multiply the number of patent experts holding the opinion.

In any event, that view was based largely on the premise that no-one is going to want to get into litigation with a corporation as powerful as Facebook. But that's just speculation with no evidence to support it.

In fact, if a developer finds that his or her intellectual property has been used by Facebook, that claim would probably be worth hundreds of millions (if not billions) of dollars. Even the most impecunious developer would have no difficulty at all in finding an attorney willing to represent him or her on a contingency fee basis.