Let me accept at face value the claims of innovation. Now securitization goes back decades, if not more. Bank letters of credit and bill discounting are both forms of credit insurance, and they go back centuries. So I'm skeptical that Wall Street has innovated rather than merely created an impenetrable smoke-screen of complexity.
Mind you, my skepticism is tempered by my own experience in finance, working on Eurodollar syndicate loans to Latin America in the late 1970s, in the first heady days of large-scale international finance since the collapse of such markets in 1914. For those too young to remember, every single one of those loans went bad, taking the economies of a continent with it—and giving regulators the option, which they failed to exercise, to shut down Citibank. Instead forbearance was the game of the day. But at the time they were marketed as safe. First, syndication allowed banks to diversify their risk, since the organizers could sell off the bulk of what were for the time very large loans, while those purchasing it were doing so in bite-sized chunks from different borrowers and different countries. Second, banks could hedge their funding and maturity risk, because while these were long-term loans (one I worked on to a "greenfield" Brazilian steel venture carried a 12-year term) the interest rate was reset every 6 months against LIBOR (the London Interbank Offer Rate). If interest rates bumped up a bit, banks wouldn't face the potential disintermediation that was at the time plaguing savings and loan banks. (Remember your history?—the plague is typically fatal. It's an appropriate adjective.) Banks didn't even need to boost their deposit base, but could borrow in the very same London market, arbitraging their good credit ratings (LIBOR) to lend on to Brazil (LIBOR+25bp at the peak of the bubble). Sound familiar?
Anyway, what are the claims made for securitization, credit default insurance and the like? The fall into two main camps, that these innovations lowered the cost of finance, and that they provided finance to borrowers who for one reason or another lacked access.
If we look at the macroeconomy, did firms go on an investment boom? No, to the extent that we'd label the last decade of growth "robust" (which requires ignoring what happened to wages), then the sources were consumption and exports. If all of these new products lowered the cost to borrowers, it's not there in the data, or at least not enough to show up without resorting to fancy econometrics.
How about access? Well, sure, lots of new borrowers got money up front, but we have incontrovertible evidence that those who received sub-prime "mortgages" couldn't handle the payments. (Not that a "3/27" ever made sense as a loan; such "mortgages" were never anything more than a bet that real estate prices would continue to appreciate). Now we're starting to see other sorts of borrowers. The most prominent right now is credit card debt, but commercial real estate loans are starting to go bad. Losses on local and state government debt, another area of innovation, will surely follow. So improved access turned out to be a short-run illusion. And this shouldn't be a surprise: back in antiquity, in the 1990s, it wasn't as though banks enjoyed zero rates of default on their portfolios. They took their chances, but generally were able to pay for their mistakes, rather than needing bailouts.
Innovation in finance ought instead to be looked upon as fool's gold, which can only be sold to the naive. (And remember the age of those "in the game"—naïve was apropos.) The essence of banking, and of finance in general, is the proper measurement of risks. We've had claims of a "new world" in finance since the days of the South Sea Bubble. But underlying cash flow analysis isn't a matter of rocket science, it's a matter of wisdom. Who knows what the risk characteristics are of a new product?—initially, no one. And how do you regulate it? Too little and too late. New products arise in the shadows, because finance is a very mature product, and there just isn't anything new under the sun.
To conclude: there is a smoking gun. It's too soon to tell, however, whether a conviction of involuntary manslaughter will follow. For those wielding the gun committed crimes against multiple economies, killed their employers and robbed the wealth of millions of unsophisticated citizens. But the outcome will likely be a mistrial: the defendant has bought off a lot of potential judges and jurors and remains able to buy expert witnesses sufficient to shout down the prosecution.