Hmm it's up to you really, most of the time i add buttons i like in my website and that's it xD people also added mine to their site without me knowing, which was a pleasant surprise when i found out :B some people tell me when they add my button, which is also really nice
i usually dont but they know, cause i put out a post asking who wants their button linked every once in a while
oh my gosh thank you : ) !!