Apparently, their marketing efforts try very hard to make everyone feel special: I've just received an email exactly like the one mentioned in the blog, congratulating me: "You were one of our first million members in Hong Kong." I don't even use LinkedIn, that's just a dummy account with no information.

I can imagine their marketing department trying very hard to make sure they find some kind of positively-sounding (but ultimately not very interesting) stat about every single account so they can justify sending that email to everyone.