I have a friend who is a private eye who has a bunch of fake profiles and uses them to find the locations of people who are running out on their bills. If he's looking for the whereabouts of an older guy for example, he has a profile that is a 21 year old college girl - and he just friends whoever he's looking for and they usually almost always accept. Then these people tell their friends where they are going, private eye drops a gps tracking device on their car and "follows them home".
Rule 1 - if you are running from someone be weary of whoever just comes along and wants to be your friend.
The DEA's problem is they are using much more complex methods of getting people to friend them - they need to realize people are idiots and will friend whoever friends them.