That's a different reason than the sentence Sharon asked you on to provide proof of:
For the record, I believe the first paragraph of yours that I quoted in this post is a legit reason. I often link to MR Deals threads on Facebook, which brings new folks to FT (though I'm not aware of a single person that stayed to become an FT member; they've all just booked the deal and never visited again, to my knowledge). (Often in the heat of a mistake fare, my friends are better served by getting the raw FT feed than trying to get info through me via FB comments.) However, the heat of a mistake fare would not be nearly as hot if MR Deals required registration.

Despite agreeing there are certain disadvantages to requiring registration, I believe the benefits outweigh the downsides.

As in every area of life, power is preceded by knowledge and responsibility. (Spiderman's uncle had it right.) The reason FD gurus don't hand $300 RTWs to newbies is that they don't have the depth of knowledge to not kill it. They may be ever so well-meaning (or ever so selfish), but their lack of knowledge alone disqualifies them. The same goes for eye-popping double-dipping tricks and promo stacking (of the sort that allowed me to pick up 1mm DL miles at under 2/10 CPM a few weeks ago). To me, these kinds of restrictions are not being cold and hostile to beginners, it's simply for their own good and the sustainability of the community as a whole. I'm a relative newcomer to FT (signed up in 2009) and I've scaled the ladder by hard work, being helpful to others, and building relationships (despite having never been at one of the magical DOs yet!). I've found folks to be very helpful (and that includes the people that get the worst rap for being the most secretive) if I put real effort into finding deals and being helpful to them in return (or rather to start with). There is a clear hierarchy of secrecy: Step by step FT/blog posts with screenshots, abbreviation-dense FT posts, coded FT posts (Trick it), private lists and forums, and finally one-on-one sharing based upon trusted relationships. All these levels are interdependent. The existence of each level depends on the levels on either side of the continuum. The fact that you may find yourself at a certain level does not mean rejection by the more secret levels; I've found the process of moving up the levels of secrecy to be a very egalitarian meritocracy. Furthermore, my experience with the people at the top of the hierarchy of secrecy is that they're glad to help newbies on the newbie level of help. (There are simply different appropriate venues for different types of deals.) As a person builds their basic travel knowledge, they automatically move up the scale. If they're friendly, they may receive a few boosts along the way. (I'm very, very loyal to two FT members that gave me two key boosts along the way. I still watch out for MRs or deals for their specific travel habits and send them their way.)

Obviously FT (IMHO) can never attain the highest levels of that hierarchy of secrecy. However, it can make itself more relevant and central to the travel world by vertically integrating its way up that secrecy ladder in small steps. Requiring registration is a step in the right direction. Having 180/180 requirements would be another. Even OPs having thread-level control over their threads as being Google, registered user, 90/90, 180/180, or FT Evangelist, I believe would have some merit.

No matter what FT does, those further levels of secrecy will exist because they are inherently necessary for the sustainability of the community. FT's choice is whether it wants to be a part of that or whether they want to let the ad revenue and page views and expert community members go elsewhere.