That's pretty debatable and I will actually walk out of a store if staff continue to bother me
after I have already politely said I do not need help. I have found that this happens all the time in consumer electronic stores. They circle you like vultures and butt in and explain things even after you have said you don't need or want their assistance.
Thank goodness for Internet shopping. Whenever I can I buy online specifically so I don't have to put up with sales people like the ones described in this article.