I don't think they sat on it for months, but days. What I think they did was to anticipate that ACORN would come out, as they did, and proclaim the first incident to be a fluke and say it could never happen again, and then fire the employees.
             That's exactly what they did, so the journalists came out with a second tape. ACORN floundered around for a while, and then became indignant and threatened to sue. I think the journalists anticipated that as well, and then un-canned a third tape while announcing that they have even more evidence.
             Now it looks like ACORN can either go away quietly, or face the wrath of the additional evidence. The ball is in ACORN's court.