Quantitative criteria are necessarily backward-looking. Therefore I don't particularly favor quantitative criteria to establish a new forum. The TB may be convinced that a new forum will draw traffic, and the TB should be allowed to use its intuition on this. (For example, I favored creation of the VX forum, even though I'm disappointed in the process by which it's happening.)

OTOH, quantitative criteria are quite well suited to helping decide whether to remove an existing forum. Although the specifics may be hard to settle on, I favor using quantitative criteria that will trigger a TB vote on deletion of a forum, with a 2/3 majority needed to retain the forum. This way the TB can keep forums that are clearly valuable but for some reason fail the quantitative metrics.