Delicious allows users to put a permissive license on their RSS feeds, so (IANAL and within reason) you can probably get those bookmarks and importantly tags. So how closely would making recommendations per tag match your idea?

Tags are a little messy, and perhaps overly specific, so you may need to cluster them and then do recommendations on that.

I'm not sure I understand how you plan on making 'influence' work, if someone bookmarks a link recommended to them do you simply increment all those who have bookmarked it before?

Please don't use the word incentivize, its terrible :)