With your job, it makes sense to have repeat customers. They add you on facebook or whatever because you've obviously built up a good repertoire with them....either that or they want easier access to you to fix their problems if you aren't at work.
Besides, isn't it better for your commissions to have repeat customers...?
I picked the "THEY ARE STALKING YOUUUUU!" option though because I'm paranoid.
When I worked at Starbucks, there was this one guy who would always come when I was working. One day, I was being a substitute for someone at a DIFFERENT store, and the guy apparently asked where I was that day, and actually showed up at that store to get his coffee and snack from me instead. It was weird.