Privacy in bookshops is completely imaginary

I have no idea why people try to talk to me in public.

This isn't a frequent occurance, but sometimes I'll be sitting (usually in Borders or Starbucks) at my computer internetting and some dude will come up to me and tap me on the shoulder. At first, naturally, I'll think it's someone I know. This would be welcome, because many people I know come to Borders and I know few people who don't go to Starbucks. Nope! It's some dude. Just some random person I've never met and will probably never meet again. They will ask me things like 'Where'd you get that computer!?' or 'Where'd you get that jacket!?' or 'What are you listening to?!' (thankfully, the latter has never happened, but I'd not put it as 'unlikely as hell').

Honestly, I don't have a huge problem with this when it's prefaced by 'Excuse me' or 'sorry to bother you' or 'can I ask you a question?' or a combination of the three. However, this is rarely the case. It's usually 'Where'd you get that', lunging right into their bloody topic that I don't want to talk to them about. Then they proceed to talk to me even after I've answered their question (I tend to answer them in a fairly standoffish fashion to see if they'll go away; they don't.) usually for a minute or more. Yes, I know, a minute is not what one would call a long period of time, but damn it if I value my minutes, and especially ones in which I want to have my privacy.

Just because I'm in a public place doesn't mean I should have to sacrifice my personal space and listen to people talk about stuff I don't care about. I know for a fact that if I wanted to piss off random people, solely for the purpose of spreading irritability throughout the city for a day, I would randomly talk to people who are sitting in public places, minding their own business. I would walk up to families and say something random, like 'how about that weather' or something equally irrelevant that families eating dinner together wouldn't want to be interrupted for. I'd make it clear that I'm in possession of all my mental faculties and proceed with annoying the hell out of them.

On a tangent, why is it that when people see someone wearing a name tag and wireless with attached earpiece (the kind that only employees of stores wear in their workplace) they go up to them (not the problem) and say (this next part is the problem) "Do you work here?" Quite frankly, no I don't, I just enjoy wearing the name tag which I shouldn't have been able to get without first at least breaking in to the back room where they keep spares of such things.

This isn't something specifically related to my current workplace. This happened when I used to work at National Electronics Superstore. We were provided (and by provided I mean we had to pay for them out of pocket) blue polo shirts for the uniform. They had the name and website of our employer monogrammed on them, of course. Nevertheless, with that fairly obviously on the shirts, the shirts fairly obviously on the employees, and the bright yellow nametags also fairly obviously attached to the shirts, we would frequently be asked if we worked there. I just don't get it. It's not even the problem of people not reading, because the colours, I would think, should take care of it all. I know that when I see someone in there wearing the company colours, I sure as hell think "He works here; he can either help me or help me find someone who can".