I usually have at least $50. I hit up an ATM for $200 every week, then spend that till it's gone.
I hate to use plastic for small amounts. I know, old fashioned. But I think I'm also secretive... I don't like leaving so much information about my shopping habits everywhere! I figure once it's out of the ATM, it's my running-around money.
Those of you who worry about someone stealing your cash... don't you worry more about someone stealing your credit card info or getting into your bank account through a debit card? The less I use plastic, the less I figure I'm likely to suffer financial identity theft.