The problems with this feat are:
1. We don't know when Loki got his hooks into Selvig - did he get him alone for 2 days beforehand and magic him up? Was it real-time during the scene? Did he have Mystique pick Selvig up in a bar and shoot him in the ass with a giant syringe? We have absolutely no idea.
2. We don't have any idea to what extent Selvig was controlled. Was he Loki's bitch, lock, stock and barrel? Was Loki just feeding him some light suggestion (since the words aren't that far from what Selvig would have said himself)? We don't know, since the only "control" feat was Selvig repeating what Loki said in one phrase.
3. Finally, we don't know what the range for this was. We know that Loki can go invisible - he does it frequently in Thor. So, was Loki actually in the room, just invisible? Was he projecting himself from across the universe? We don't know that, either.
This makes it a pretty hard feat to use in a rumble.