The idea is to allow embedding webpages and once the slide is shown the webpage is loaded live and shows it's latest state. There are many use-cases this would be very interesting for.
It is a feature I personally have been looking for many times. MS office neither has it. But there's a plug in for the windows varian of MS Office that does just that: http://skp.mvps.org/liveweb.htm
Maybe an edge case but every other month I keep ending up wondering that this would be just what I need and why it isn't there. :)
NEW :-). We discussed this on IRC.
Valid enhancement request.
Thanks for filing an enhancement request James ;-)
*** Bug 70193 has been marked as a duplicate of this bug. ***