In a public place  you are wide open to having your photo taken and used on the net  or published without your permisssion.  the press do it all the time, Sure someone can object but theres nothing they can do legally. Provided the caption is accurate. With the huge growth in the use of mobile phone cams its happening more often than you think. And of course you have to be sensible in how you frame the subject.  Like avoiding many pics of possible sexual content.

I am amused at how reaction varies from the public depending on what camera I am using. I am ignored  when using the phone cam, mild interest when a compact is seen , but a lot of questions when i use an SLR with big flash visible.  The press pros get similiar reactions when they go out to cover a parade on a public street, they have had police hassling them while Joe public is ignored even tho the public are using good resolution kit and just as likely to publish pics on line .
Life is full of double standards.