While the pictures are certainly intrusive, I happen to agree that if Kate is going to go out in public and shop, than she should expect that pictures will be taken. If its not the press who took this picture, but an employee or someone shopping at the same time....trust me...they made a pretty penny from this picture...especially if is sold overseas. A while back I read in the Washington Post magazine about a company that deals with ordinary people who see stars, celebrities and/or well known people and take pictures. If you take a candid shot, you can certainly upload it and they sell it on your behalf. So its not just the professional photographers who have an interest in selling pics.
I think it becomes a problem when she is stalked like Diana was (and it appears Pippa is now), when every time she goes out and about someone is following her. It does remind me of the frenzy that first happened when Diana married Charles and she couldn't go out without someone following her and taking pictures. I believe someone from BP complained and asked if it could be toned down a bit (not stopped just relaxed) and someone (from the press I believe) simply stated that if Diana wanted to go to the store and get chocolates, couldn't she send a servant or something like that. Apparently, the look they got in response was quite priceless.
That being said, does TESCO have home delivery? With Giant (a grocery store in my local area) you can order online and have it delivered to your home. Of course, its not the same thing as picking up your own produce. But there you go.
As someone said...they are not normal so they should just move on from that concept.