That idea got me to playing around with md5sum and "uniq -cw32" in my
netscape cache directories.
I turned up 700+ suspiciously duplicated half-K files, of which at
least 300 were one of 3 variants on "Visit Amazon.com Auctions
today!".
As you point out, not a waste of disk space in this day and age, but
I was feeling sufficiently the curmudgeon to give doubleclick a special
hostfile entry.
-Dave