I know exactly what you are talking about. I've been on MKA online a couple times and have seen these cheap ass KAK combos. Neverending combos like infinates and stuff are usually mere glitches and only happen at certian times for no apperant reason. Online has been known to fuck up and slow things a bit which leads to random effects like combos exceeding their hit number,damage dealt when no one throws a punch,and extended air kombat and juggles. It's pretty much all glitches and random effects to my knowledge. Seeing as in KAK fighting styles the max number of hits you can get in a combo is 4. (With a certian kick) Usually if you combine a good combo with a popup and juggle,then add air kombat you can get a 8-13 hit combo. You have to kinda play around with the system to get different ones.

Search YouTube. They have broken combo / KAF's all over the place in vids.