My thoughts on the matter:
I don't think wood bats are any more dangerous than an approved Freak 98. In fact, I think that their performance is typically just above that of an Easton Hammer.
However, the letter of the rule is clear: all bats, regardless of whether they're composite, metal or wood, must meet the qualifications of ASA Rule 3-1. If I think it's pre-2000, it doesn't need the stamp. Otherwise, it must have the stamp.
And since ASA is certifying wooden bats (such as the Viper), I believe that further reinforces the argument that ASA does not view wood bats any differently than composite or metal bats.