Let me suggest a compromise - in fact, the system already exists.
Most people will want to see a particular species nearest to where they live if only to minimise travel. Yes agreed, a Marsh Fritillary in Cornwall is the same as one in Hampshire, but for most enthusiasts, it is far easier (and more environmentally friendly in terms of travel) to see them in Hampshire.
As is pointed out, many of the sites for rarities are in the public domain. I know localities for ALL resident species, so it's certainly not a case of needing a "tick" (to use birding parlance). Many enthusiasts on the group will be equally knowledgeable but not all and we must remember those who are relatively inexperienced and give all the help we can.
So my compromise suggestion is this. If a species is really rare, eg Marsh Fritillary and it is considered by some that localities in say Gloucestershire are best kept confidential (and as you know, I don't agree with that, but there we are) then it could be reported for example that "In one of its Gloucs localities, 17 males and 12 females were seen in Tetrad SO90G"
(that is not necessarily a genuine site - it's more or less picked at random)
Explanation and conversion to tetrads:
http://www.bto.org/birdatlas/taking_part/gridrefs.htm
This preserves the degree of confidentiality that many are arguing for but is passably satisfying for those like me simply want to know that the species hangs on in that locality and is apparently doing well.
Incidentally, I find the idea of conducted visits by members of the "in-crowd" is abhorrent. Again it suggests that some people can't be trusted if they visit on their own. If someone is taken on such a conducted tour, he will of course then be in a position to reveal the locality so any confidentiality is immediately lost. (Unless we have the equivalent of a Butterfly Official Secrets Act). Why not simply give the locality in the first place?
I don't especially want to know the locations of every sensitive site FOR THE PURPOSES OF VISITING as I am unlikely to be able to go to more than a handful. But I want the RIGHT TO KNOW even if I never use that information. So in summary, although far from happy with downgrading site locations to mere tetrads, the tetrad system is already in place and might offer some sort of compromise.
Jack