The list you refer to is annually published in Conde Nast Traveller. They have stated (on a Flyertalk thread in another forum) that it is an unbiased list; i.e., no one buys their way on to the list.

The agents typically referred to here in this forum, particularly for hotel bookings, are Virtuoso or Four Seasons Preferred Partner agents. There is already a recent thread on this topic and I am going to merge this one into it.

RichardInSF, moderator, luxury hotels