One example on how an object graph is serialized uses the 6 degrees of Kevin Bacon game. Just the other night there was an ad for Visa or Master-card or something (shows how ads affect me when I can't even remember the product!) that stars Kevin Bacon. To proove his identity he runs around finding people he knows, and people they know to connect himself to the merchant.
The other funny thing about this is while I'm watching the ad my wife says, "yeah, well our friend Franc knows Kevin Bacon".