grizzy if your eTrade account has a value of more than 25 grand and you have a margin aggreement then you have what they call (margin) buying power that exceeds the cash amount in your account.
When you use the (margin) purchase power you are in effect buying on margin and they can then force a margin call against you. So if you are trading always use the cash amount unless you want to get into trouble and have a possible margin call that will cost more in the long run especially if the stock downtrends from where you purchased it.
And yes the brokerage can force the margin call at any time and they can sell any of your securities if that occurs to cover the margin call and its perfectly legal.
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