Is it wrong for birth parents to track down kids they gave off for adoption on Facebook?

[Lover]

When people have kids and give them away for adoption, do you think it is right or wrong for these people to later down the line contact the child they gave birth to through Facebook, i.e. by sending them friend requests and messages introducing who they are? Because I've heard of some teenagers one day randomly logging onto Facebook and suddenly seeing the shock of their lives seeing their birth mother sending them a message and saying who they are, etc.