How Many Promotions on Twitter will Be One Too Many?

My first reaction to seeing the Lucky logo at the top of my tweets was to wonder when I  had added Lucky stores to my network and how to "unfriend" them as soon as possible. But, alas, it was a promotion by Lucky Supermarkets. I wonder how many of these links in a row will drive us from reading the un-promoted links below?  Two or Three or four or more?