Sometimes you may be worrying about your profile picture is using by someone else, it could be in social networking sites like Orkut, FB, Myspace..etc.
To find out if someone is using your picture on his profile check this website, using reverse image search. It is free to use and might return some unexpected results, so don’t be too much confident that you’re out of grid.
This is the website: Click Here
Note: You can go even further and look not only for pictures of you but other picture taken by you. You might find some of these used without your permission on others websites photo galleries. :-o