Performance issues in 'hot linking'. This new server naming is also used for 'hot linking'. You do 'hot linking' when, for instance, you post a direct link to an Atpic picture from a forum. The old direct URLs were built as follows:http://direct.atpic.com/UID/GID/Secret/PID/Resolution.Extension
When a lot of users were posting images in forums using those URLs, the overhead generated by looking up on what server the picture actually was, was causing big performance issues. The new URL format is: http://uUID.direct.atpic.com/GID/Secret/PID/Resolution.Extension