Bernanke Burns the Bulls

With risk tolerances this high, maybe this is a good moment to investigate what could give the markets problems. Doomsday scenarios aside, there are a few threats.

It could be the "ungluing of the carry trade," as Leverage World CEO and publisher Marty Fridson notes. Investors looking for an example of such a scenario might consider Iceland, where capital was pulled out of krona-denominated assets in droves after the country's credit quality came into question earlier this year. The country has a current account deficit amounting to roughly 16.5% of its GDP.

If Japan raises its interest rates, the carry trade could take more hits, said Fridson.

The dollar's current selloff certainly doesn't make U.S. securities more attractive for foreign investors. The dollar slid to a six-month low Monday against the yen, to 113.35, as fears mounted that the Bank of Japan will raise rates for the first time since 2000. The 10-year Treasury fell 17/32 to yield 5.13% Monday.

"Threats to our marketplace may come from shareholder activists or a Fed that comes back to hike rates aggressively," says JPMorgan's Marrinan. He added that anecdotal evidence suggests corporate credit investors are most concerned about geopolitical problems roiling the current market momentum.

Meanwhile, light, sweet crude oil rose $1.82 at $73.70 per barrel amid the conflict over Iran's uranium enrichment program.

But like functioning alcoholics, perhaps U.S. markets can stay on their feet -- even with these risks in place. The proliferation of credit derivatives and hedge funds has given risk a happy home, for example.

"There are plenty of things to be nervous about, and it is counterintuitive to people that we're not sitting on the edge of a volcano," said Fridson. "But we may be having the same conversation a year from now."

Against such a backdrop, the Fed's slow and steady monetary tightening may require an unexpected shock to augment the lagging effects of its 15 hikes thus far.