It would be a convenient way for the browser to rank all of the
possible paths from the current document and therefore do prefetching.
In other words, if I (an information provider) know that the link
"General information" on the NCSA home page is the most common link
selected by people who access the home page, then I could use this
FREQ attribute to encode that in the document itself and therefore a
smart browser could prefetch whatever's at the other end of that link
each time (or the first time, or whatever) a user accessed the home
page.
(I think this shouldn't be part of the markup language; however, it's
fun to think about how it could be pulled off otherwise. I'm in favor
of a local agent that watches all dataflow in and out of my system and
can therefore learn to predict what I'm going to do next.)
Marc