I can see it being a good choice for drive by shooting tactics. Not Detroit gang banger tards, but the guy riding bit@# in a hum vee in Iraq. I've seen quite a few guys using stumpy versions of AK's for this. I'd take the 7.62x39 their using over a baby AR for this though. Regardless of magazine interchangeability between the baby AR and the MP4's they all had next to them as well as the baby AK's in their hands. You didnt see the baby AK's leave the vehicles. Thats when the MP4's came out.
Some of our guys have been carrying "pick up" AK's in place of issued rifles too... Hmmmm.
I'd guess the average grunt would catch hell for this. No idea if these were special ops or what. But they were our troops, not contractors. The contractors can be seen carrying everything under the sun.