I have never had a problem taking someone else through with me in the elite security line -- I always put my boarding pass (summit) on top. In some cases we are booked on the same itin, while in other cases we are not. Never had any sort of issue.

Generally...and this is just a personal thing with me...I usually don't do this with work associates, just with my SO. We have different last names, however, so TSA wouldn't know who the heck I'm bringing through with me, and it's never been an issue.

Same thing with early boarding at the gate...never had any issue.