The systemic margin call extends to a portion of the market most of us actually understand: home equity loans.

NYT: Americans owe a staggering $1.1 trillion on home equity loans — and banks are increasingly worried they may not get some of that money back.

To get it, many lenders are taking the extraordinary step of preventing some people from selling their homes or refinancing their mortgages unless they pay off all or part of their home equity loans first. In the past, when home prices were not falling, lenders did not resort to these measures.