I've been wanting to use my recent birthday present lens for some candid photos of people eating and drinking. Yesterday I spend a half an hour people watching at a market. You can see the entire set by going to my Flickr account here.
I've checked and it is okay to publish photos of people taken in a public place, without their permission, provided they aren't shown in a detrimental manner. If your photo is shown and you object it can be removed.