Essentially it means "pinging" another server to let it know you are linking to it in an entry, which in turn forms a bridge between the two articles which can then be used to navigate between the sites. The origionators, MovableType have a stab at explaining it here, there is also a pretty simple explaination here curtosy of cruftbox.com and a more technical one here curtosy of hitormiss.org.
LiveJournal tentatively entered the wider world of "blogging" when RSS aggregation/syndication was developed, allowing for the first time external sites to have any influence what is shown on LJ's pages. Could TrackBack interaction be integrated to further that development? Afterall possibly the biggest attraction for using LiveJournal is the feeling of a true community, this would just extend that.
According to MT's article TrackBack has been implemented into quite a few of weblogging tools, I can only assume that more and more will take it on aswell in the future. I personally see no reason why LJ should be left behind.
Of course implementing such a thing on a site the size of Livejournal would be much more difficult than it would be on a single user site. Database load from a lot of pinging activity could be quite high as it wouldn't just be LiveJournal's userbase being dealt with, but that of the entire blogging world. Still, it's certainly not impossible and LJ always has the option of limiting to the paid userbase.
Does anyone have any thoughts on this?
(note, this is not intended as a full blown suggestion but an invitation for discussion on the concept, is there anywhere more appropriate I should be posting this?)