Bird Dog
The person in a group of friends who has the dirt or info (the 411) on anybody else. whether they be part of the group or not. The bird dog of any group usually has the capability (techinical know how) to seek the info needed.

Bird Dogged
Bird Dogging
You realize hes bird dogging your buddy over there. he just told me about his two felonies and was going on about his past girlfriends