One thing to remember: Using FB isn't/won't-be instead of WTW -- not for most of us, anyway (I predict).
I think it's unclear how it will be used...but I, for one, don't feel that WTW-on-FB is any danger to WTW. I'll go on the record to proclaim that my prediction will hold true.
I, too, noticed that I can see the "real" identities of some WTW members who've "Liked" the WTW FB page (a number of well-respected WTWers, by the way). As Lighthawk points out, that's a FB thing.
But: You can lock down your FB profile so that only those you've marked as "Friend" can see anything about you, other than your name. That's how I have my profile set.
FB deliberately makes it non-obvious/difficult to increase privacy settings because increased privacy means fewer page-views and fewer page-views means fewer eye-balls looking at and clicking on its ads. But Facebook is a for-profit business (as is WTW), so this approach doesn't surprise me nor do I resent it since I have the right to chose to not use FB. (My retirement is dependent on investments in for-profit businesses!)
(PM me if you want to increase your FB privacy settings and don't know how.)
I frequently criticize Facebook -- on Facebook, and yet I look at it every day and post on it several times a week. If I really couldn't stand it I would delete my profile.
That's the thing about Facebook: If you don't like it, don't use it -- problem solved -- it's as simple as that.