I lock squads for a few reasons.

I have Vent hooked up for all the BLKOPS guys and it makes it easier for us to hear each other if theres not 5 randoms talking over the SL.

If I start a squad at the start of a round people will join it no matter what its named. If I start a squad named "Tank 1" knowing that Im gonna grab a tank with two other people than Im cheating the team by having more than 3 people in my squad. If I let the squad fill up than thats 3 people who will not get a Rally point all round. and one less for the team as a whole.

Ohh and if you start mouthing off on VOIP or act like a douche in general Ill lock the squad and kick you.

Thats about that