I'm not supportive of this. FlyerTalk is about the sharing of information.
Things like this help turn lurkers to members.
You win some, you lose some.
Having someone logged in or not logged in isn't going to help the problem (assuming you believe there is a problem, I don't).
At this time, I don't support anything that makes FT more restrictive. I don't believe that was in the interest of the founding principles of FlyerTalk.