I had entered into a game of team instant action and went on a 5 kill streak only to realize that none of the people i had killed dropped their dog tags. i thought that this was strange and figured it would fix after i had finished the match. i then entered the next match and experienced the same thing. i backed out of multiplayer and re-entered only to have the same thing happen. i switched to my sniper class with retriever and had a 7 killstreak but still hadnt collected any. i guess i will find out if it fixes when i play tomorrow.