I had assumed that you were proposing being able to "mark" a node as something you like....sort of like I can mark shows I like in TIVO and it decides to record suggetions based on my preferences and habits.

Marking a node that you like would be pretty easy, you could even just use the current voting system as voting up a node assumes you like it (allthough I hear that some folks use votes to gain XP or affect others XP <grin>)

the challange as I understand it is then parsing new nodes to offer the users suggestions on nodes they might be interested in....this is where I would imagine the most significant amount of overhead to the system.