If I'm lifting heavy or maxing and need a spotter, I find it easier to have someone I know, versus asking some random gym person. That way I know they can support the weight I'm moving, and it won't be dropped on me if I need the help.
But for my standard lifting schedule, I prefer to lift alone. Less distraction, less time wasted, less criticism to give and take.
Mt Snow, VT - May 5, 2012 - Completed!
...i remain, he who remains to be...