Negative amortization loans have been around for a long time. They are pretty easy to understand. The lender will allow you to pay less than a fully amotized payment for a certain lenth of time as long as they feel you have enough equity in the home (via down payment, etc) and a stable or growing income.

The “exotic” loans that everyone has panned are those made to mostly subprime or to people who had no means to repay the loan once it reset. In most cases, they were 100% LTV so there was no equity to protect the lender. The brokers who pushed them in many cases lied on the credit app about the borrowers income and assets. Dumb business practices by the lenders and criminal behavior by the brokers lead to tons of losses and pain.

As with any investment or purchase, if you don’t understand the terms then don’t buy or invest.