Joe Hummel probably told Goodell to go...well, you know....
He was probably having trouble sleeping at night, knowing he was raking the Saints over the coals. His conscience was bothering him, knowing how many lives he was affecting with this whole bounty BS, and he was probably asked to find SOMETHING on the wire-tap BS, and he had to resign so that he could somewhat look at people with some kind of dignity. Now his life is turned upside down, maybe even ruined, all because of the vandetta that Goodell has against the Saints.

Guck Foodell!

This is a slippery slope... Obviously we would love for the reason to be because he may have fabricated something about the Saints... However it may also be because the NFL told him to hide something that would implicate the rest of the league or other teams...

He may have been told to ignore an email from Goodell chipping into the pot.

UPDATE 4:00 p.m. ET: The NFL contends that Hummel wasn’t running the bounty investigation, even though his title is “director of investigations.” Regardless, two men primarily if not exclusive were involved in the probe: Hummel and NFL Security chief Jeff Miller. Thus, even if the “director of investigations” somehow was not directing the investigation, Hummel had an integral role in the process. “He has worked extensively on the investigation,” NFL spokesman Greg Aiello said via email. “He reports to Jeff Miller, who is our chief security officer.”

Doesn't matter. We need local news, paper and television to CONTINUOUSLY REPORT that the major outlets like ESPN and NFLN aren't reporting this at all.

I read somewhere he got hired on as the Director of Security for some large corporation, but agreed to stick around until the bounty case was completed. It may be a simple case of "better job, move on."