QuoteIn fairness, Lott notes that pressure from disclosure worked in both directions, if not quite equally:

QuoteIndeed, supporters of Prop. 8 engaged in pressure tactics. At least one businessman who donated to "No on 8," Jim Abbott of Abbott & Associates, a real estate firm in San Diego, received a letter from the Prop. 8 Executive Committee threatening to publish his company's name if he didn't also donate to the "Yes on 8″ campaign.

Lott notes that civil-rights groups benefitted from donation anonymity in the past.  The NAACP had to fight Southern states all the way to the Supreme Court to keep their donor lists from going public, and the NAACP eventually won.  More to the point, Lott points out the dangers that may arise unrelated to the campaign donation itself.  When an animal researcher donated $500 to John Edwards, her address got posted to an extremist site with several others under the heading, "Now you know where to find them."  Would full and instant disclosure result in exposing people who ran away from abusive spouses, for instance, and intimidate them into opting out of the political process?