On 10/23/05, Timwi <timwi(a)gmx.net> wrote:
LiveJournal did the same originally with their user
picture URLs. I
realise they ran into the concern that it would allow people to
enumerate all user pictures, giving an easy way to write a good-faith
script that would kill the servers. As a counter-measure, they added the
numerical ID of the user the image belongs to to the URL as well. Since
that never changes either, you still have the nice 'permanent URLs' effect.
We also hardcoded the image-serving httpd to immediately respond with
a 301 if the request had an If-modified-since header, which made a
huge difference in traffic. (But LJ has a lot more "reload" traffic
than WP does, I'd expect.)
One advantage of using a hash (instead of a timestamp or an
autoincrement secondary key) as a guid is that multiple uploads of the
same image can be stored as one instance. I guess it depends on
whether duplicates are a concern; for example, how often is the one
goatse image uploaded?