No boss, in banking at least, is as candid as Dimon — as we’ve learned at Fortune over the years, and the Summit attendees discovered the same. Dimon shared loads of wisdom that’s helpful to managing in the market meltdown. But I particularly liked his recollection of landing his first CEO job, at Bank One, eight years ago.

“I was terrified,” Dimon said. Chicago-based Bank One was a mess, and he had to slash at least 10,000 jobs and the dividend too. Having been fired from Citigroup by his mentor, Sandy Weill, he was navigating a land mine with a couple of other ex-Citi execs by his side. “They told me, ‘We can’t do what we need to do — make these cuts — and take a bonus…And if you give me a check, consider it severance.'”

Dimon not only withheld the bonuses for those two execs and himself that year, he also asked his top 15 people, “What do you think you should earn?” He then yanked their bonuses and a swath of perks, including club memberships, car services, even matching gift grants. “I told them, ‘I didn’t do it to punish you. I did it because they’re all entitlements. When the company does well, I’ll pay you even more.'”

As we know now, Dimon saved Bank One and merged it with JPMorgan Chase, becoming CEO of the parent in early 2006. Those execs who agreed to suffer along with Dimon are now on his team. “Leaders emerged,” he said. “And some people hate your guts for the rest of your life.” Those who stuck by Dimon turned out to be, as my colleague Shawn Tully explained in a September cover story, the best-positioned in banking — healthy enough to acquire Bear Stearns and Washington Mutual on the cheap.

Now, will Dimon follow the top brass at Morgan Stanley , Goldman Sachs , and Barclays in giving up bonuses for 2008? There’s no official word from JPMorgan Chase yet. But people close to Dimon say that, knowing him, he probably will.