I know that some hard core SEOs here use PBNs to rank sites.
But there are some things which keep my mind busy.
I thought about some things which could be some footprints for SEs:
1. Using admin to post your articles
2. Private Whois: If all blogs linking to your main site have this isn't this rising flags?
3. Always using the cms
4. Having just some (up to 7) unique articles on them
Don't you think that these are footprints?