Given the current state of the forums, I believe that the reputation requirement for custom titles should be substantially lowered. There honestly is a limited number of members that can actually rep others, much less put the above-average member above the threshold for a custom title.

Put it to something like at least one full, dark green bar of rep (using the rep system in use on 1/31/12). That should be more than sufficient for a user to have earned the right to a title of their choice. That puts them well within the top 100 registered (active or otherwise) members of the forums, of which we have over 2500.