Absolutely, people change their opinions all the time, they don't need an excuse, rather, a welcoming pat on the back. It's a good thing!

I thought HN had been fairly privacy-skeptical of Facebook for a while.

Often with these things it's not the same people switching from a view to its opposite, it's more that one group shuts up and the other speaks up. The collective appears to change its mind without any individual having crossed the floor.