Bankapedia's Take:

Balloon payments rarely exist in standard residential mortgages, as they are mostly the province of commercial mortgages. However during the real estate boom of the mid-2000's balloon mortgages became popular on second mortgages. 100% loans were typically being financed as 2 mortgages to avoid paying mortgage insurance, which will occur when one mortgage exceeds 80% LTV. So 2nd mortgages where being amortized over 30 yrs, but would have a balloon payment, the remaining balance, due after 15 yrs.  

I'm sure by 2020 real estate prices will have rebounded to the point where people will be able to refinance their second mortgages, otherwise we can add one more ticking time bomb to the mortgage list.