For thirty years W. Hall Harris III has taught on the faculty of Dallas Theological Seminary in the New Testament Studies Department. Since 1995 he has served as Project Director and Managing Editor for the NET Bible at bible.org passionately steering this revolutionary Bible from inception to global impact. Dr. Harris has traveled extensively in Western Europe, especially in Germany and Italy. And as an ordained minister he has served over the years as pastor of single adults, elder, and adult Sunday school teacher.
I'm sure usage testing would be helpful. As Wayne Leman points out in a later comment, British and American usage also seems to differ here. We were simply basing our decision to retain the plural verb with the collective singular subject on the NYPL Style Manual at this point. If anyone is inclined to do some testing on this and give us the results, we'd be glad to consider the input.
Hall Harris