use of placeholder as a label for an input

The HTML spec currently states [1]:

The placeholder attribute should not be used as an alternative to a label.

should this be tighened up to MUST NOT?


I believe there are cases where having a label associated using the label
element may not be required, but can't think of any cases where the
placholder attribute text suffices as the only label for an input.

thoughts?



[1]
http://www.w3.org/html/wg/drafts/html/master/forms.html#the-placeholder-attribute
-- 
with regards

Steve Faulkner

<http://www.paciellogroup.com/resources/wat-ie-about.html>