Quote from Misthos:
Anyway, I remember hearing that assumable mortgages were quite common, and in the end, the banks suffered for it.
I don't know of too many commercial lenders that wrote them, but all FHA and VA mortgages since WWII have been assumable, still are today.
NOTE: Hmm, seems that's not a blanket statement anymore. Most, but not all FHA and VA loans in the past few years still are assumable but require lender approval.
http://www.bankrate.com/finance/mortgages/will-assumable-mortgage-solve-crisis-1.aspx