I work with VERY big pictures, PNG files with 130 MB or more (1200 dpi A3 pictures for poster usage or bigger) and I did not even notice any difference with the new 500GB hitachi hard disk (7K500) between fastfilling the zones and sorting.
Personally I consider 130 MB files 'large' and these go directly to my 'big spacehogs' zone which is not just never sorted but even not fastfilled.
But you know, majority of population does not work with such large images. The more specific usage pattern you have, the more should you be aware of the fact that what works for you may not work for everyone.
Whenever you come and write something like 'this MUST be ALWAYS done this way', please add 'on MY PC' to it. Then I'll have no comments to such statement.