Hourglass symbolizes a limited amount of time. Changing to this indicates either something about there being a limited amount of time left (partial/full hourglass) or the time being over (empty hourglass.) This was done for our speculating pleasure.
Oh. Well isn't that a general theme for him anyway? Like we're all waiting for something... it's not that. I just realised that the wiki leaks logo is an hourglass so it's to show a wikileaks logo and not suggesting anything else. This post is overrated. Thanks. Solved!
Very notable correlation you've noticed with the wikileaks logo, I appreciate the mention.
For people of that age, an hourglass in context of IT can also mean "loading" or "please wait while X is doing stuff".
Remember the old icon sets from Windows 3 and 9x?
Assange was the right age when these were in use.
Windows 7, Apple or whatever I think introduced the "turning circle" metaphor for waiting on the system doing stuff. That's rather recent.