Generate a placeholder attribute from the datalist associated with that input.

placeholderFromDatalist.js

(function(win,doc) {
	if (doc.querySelectorAll) {
		var inputs = doc.querySelectorAll('input[list]'),
			total = inputs.length;
		for (var i=0; i<total; i++) {
			var input = inputs[i],
				id = input.getAttribute('list'),
				list = doc.getElementById(id),
				options = list.getElementsByTagName('option'),
				amount = options.length,
				rand = Math.floor(Math.random()*amount),
				option = options[rand],
				value = option.getAttribute('value');
			input.setAttribute('placeholder',value);
		}
	}
})(this,this.document);

Here's the thinking behind this little bit of code: http://adactio.com/journal/5663/

How about an online demo?

@mathiasbynens Go for it.

http://jsfiddle.net/F5Z47/

@mathiasbynens Thank you!