I'm wondering how many US copyright lawyers are
participating in this
discussion.
While we're all speaking out of our butts, let me add that simply
explicating that by submitting to Wikipedia you're willing to accept
authorship credit under the collective name of "Wikipedia
contributors" would likely handle any legal considerations.
But IANAL. And it's not like lawyers actually know anything. It's all
whistling Dixie until a court rules.
It's less about authorship and more about accountablility.
We need those names so we know who to hold responsible if the info is wrong.