Hi Jim,
I guess anything is possible, but they usually give more warning than that from my experience.
I do pay attention to margins on anything I am trading or interested in trading almost daily as the info is a little mouse over pop up on my charts.

I usually take a change as an exchange estimate of a coming price move or increased(change in) volatility. So, I would keep an eye on it and be prepared to react.

I thought Corn might pull back, instead it's pretty much holding the low 780's ???
I assume you are trading/watching Corn. Any thoughts ???

Hope all is going well,
Thanks, Lee