The CDO market exists since there's a market of investors who are willing to buy tranches–or cash flows–in what they believe will yield a higher return to their fixed income portfolios with the same implied maturity schedule.

Do they still sell CDOs?

Today, CDOs have returned, although the playing field is a bit different, said Adham Sbeih, CEO of Sacramento-based real estate lending and investment firm Socotra Capital. "Today, hedge funds are securitizing and selling the CDOs," Sbeih said.

Are synthetic CDOs still a thing?

Yes, but: Today's synthetic CDOs are largely free from exposure to subprime mortgages, which drove much of the carnage in the crisis. Most are credit-default swaps on European and U.S. companies, and amount to bets on whether corporate defaults will increase in the near future.