Presumably, that source would okay the unmasking to Prior. If not, then that could really hurt his ability to get more sources. Presumptions both ways. I'd think twice about leaking the inside scoop to someone who volunteers that info in the Tribune without spelling out the anonymous source's wishes in the matter. ETA: Of course, Carroll didn't write the column, he was just interviewed for it, so it's not like he had complete control over what was written.