sticky positioning not enough?

I was browsing Cnet's web site [1] this morning and started playing a
little bit with the scrollbar to see how scrolling affects the top
toolbar. Sticky positioning does not seem enough to express such
behaviour. I started thinking we need media queries based on scrollbars'
positions but that could probably create infinite loops. Then I
saw that a :sticky pseudo-class would do the trick and would be very
easy to handle from an author's point of view. What do you think?

[1] http://www.cnet.com/

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