There exists a type of customer that is a Sunday shop workers worst nightmare, they frequent smaller or independent one person shops and exists soley to deny the worker a lunch break by not leaving.
You'll have never seen this person before in your life, or if you have they will be socially awkward and not able to hold conversation. What these people are exceptionally good at is not knowing what they want, doing circuit after circuit of the shop picking up items and putting them back in a never ending circle of futility. On the occasion they do leave they will be replaced by another almost in the same instant. By this point you'll have pre-written a "back in 20 minutes" sign for if you ever manage to escape - but deep down you know you'll never get to use it.
Sometimes it might seem like a relative shopping for others is an anonymous browser, they're not - they're just confused about what to get. Go help them, don't mistake bad customer service for a bad or annoying customer.
I've been here for 5 hours now and I had a late finish last night, I'm dying of hunger...why can't that anonymous browser go away so I can go and eat?!