Last night, Jefferies said that it expects second-quarter earnings to far surpass earnings estimates. Per the release:

"The firm expects that Fixed Income and Commodities revenues will exceed the record set in the first quarter of 2009, driven by record quarterly results in the sales and trading of corporate bonds, mortgage- and asset backed securities, rates, municipal bonds and emerging markets debt."

The firm also reported strong results in high-yield and investment banking.

I can already hear analysts extrapolating Jefferies' results to its peer firms, raising estimates going into quarter's end.

But be careful: I expect the second quarter may go down in the record books as one of the best, if not the best, 90-day periods for spread products and commodities in history. And, while I have no doubt that other firms benefited from this extraordinary market performance, it's very difficult for me to see how any of this is sustainable.

For financial services firms, earnings are the past; the balance sheet is the future. My sense is that most banks and brokerages (including obvious heavy hitters like Citigroup (C), Wells Fargo (WFC), and Bank of America (BAC)) have used this quarter to sell anything and everything they had on the balance sheets at whatever gain they could during the second quarter. Furthermore, firms like Jefferies were in a sweet spot as stock issuance boomed, with corporations and banks raising equity to repay both TARP and other debt.

While I expect many analysts will offer that the second quarter is just the beginning of the earnings recovery for banks and brokerages, let me offer 3 counter-risks:

1. While "stock may be the new debt," it's far from clear that equity underwriting (often characterized as investment-banking revenue) can enjoy the same kind of profitability it has during the second quarter's "celebration of survival." Selling equity when everyone wants it, is a lot easier than selling it when corporations need it, but nobody wants it. (A scenario that I think will define the second half of 2009 and most of 2010).

2. The Obama Adminstration's proposed banking reforms suggest that, in future, brokers will be required to act as fiduciaries. While the details have yet to be fleshed out, I would offer that there are irreconcilable differences between today's broker-as-salesperson model and the broker-as-fiduciary model -- and none of it bodes well for profitability.

3. With most financial firms focused on short-term survival and current-quarter earnings maximization, it feels to me like the cupboard is increasingly bare.

And it isn't clear that there are any earnings rabbitts left in the hat.