Online news publications need constant content 24/7/365. They often keep watch on low-level blogs and use materials they find there. It would be good to be up to date on which blogs they use often.
Do a constant crawl of these high-profile publications to discover their sources, and keep an updated list of these sources ordered by topic and probability of being used as a source.
To see visually where these bloggers are publishing their writings and get a birds eye view of their network of influence.
Write a crawler that would scan the internet and map who publishes where. Using this constantly expanding database you could see a map of influence for a specific influencer: where is his main point of influence and what other publications is he using to enhance his footprint and influence.