We've all seen with our own eyes how it looks on the servers and what has happened to our guilds and friends lists. Can they really be completely unaffected by this? For a couple of months over the summer - certainly. But I've got the feeling this has been going on for quite a while now.
You know, the odd thing here is that I do know what's happened to player numbers in our guild - they've gone up slightly, as a couple of people who have been out of circulation for months have rejoined.
Really, until Blizz starts publishing some numbers themselves, all we have is anecdote and guesstimate (even if some of that guessing is technologically driven) to go on, and that's really, really prone to selection bias.
Not arguing against anything Larisa's saying here - just raising a note of caution...