Automatic website caching.
Here is how it works. When I post in my journal and link to a website... what if that website changes and the content I am referencing is no longer available. A special entry tag could be created so that URL's would look something like this:
<A HREF="cache[http://www.msnbc.com/]">look at the news</A>
This would tell the LiveJournal server to go get that page, and any images on it... and store it for archival purposes. When the event is rendered (in a friends view, or a lastn view, or wherever) the cache[.*] portion would be replaced by a URL on LiveJournal servers that would cause a framed version of that page to appear. The top frame would state that the page was cached on XYZ date for user revjim and give the actual URL to the website. Then... in the lower frame. The cached version of the page would be shown.
Some additional measures could be taken to allow caching multiple link levels, offsite links, etc etc etc. The amount of the page that is cached is someting that will need to be worked out... but the concept is there.