Group selection is dead; get over it!
It is the sort of thing that people like, and want, to believe. Thus, though better theories supplant it in scientific usage, we may be certain that the 'hypothesis' will persist for a while as an element of folk-science. Eventually, that remnant, too, may vanish in light of discordant facts, and the essential imagery of this once-scientific hypothesis will recede to a revered position in the popular environmental ethic, where it doubtless will do much good.
PZ Meyers suggests that David Sloan Wilson has "made a persuasive case for group selection (but then [he admits], I'm already partial to the idea anyway). " This partiality is surprisingly common, despite the lack of empirical evidence that group selection (as opposed to kin selection) is of more than negligible importance as an evolutionary force in natural ecosystems.
Theory, too, suggests that group selection can be ignored. We've known since the 1970's that the conditions under which group selection can counter individual selection almost never occur, namely: ("deme sizes of less than 25... and migration, could not be too much greater than five percent per generation" Levin BR, Kilmer WL. 1974. Interdemic selection and the evolution of altruism: A computer simulation study. Evolution 28: 527-545).
It's not that group selection can't work. For example, Muir (Poultry Sci 75: 447) increased egg production by selecting for the collective egg production of groups of 4 hens (4<25, no migration!), with reduced aggression a side effect of human-imposed group selection. But in nature, a bird whose selfish behavior leads to decimation of its flock just switches to another flock. In nature, there's no human in charge to impose selection at the group level, limit group size to <25, and prevent migration between groups.
Kin selection theory generates lots of experimentally verified predictions every year; group selection none (under nonartificial conditions). But people want to believe in it because it makes them feel good. Sound familiar? Group selectionism is a religion. (The quotation above is from Goodman's 1975 paper "The theory of diversity-stability relationships in ecology", but seemed equally applicable to group selection.)