As a web master of a very small, personal site, I find that running AddThis or something similar to be vital in generating traffic. Giving users a one click option to share my pages makes it much more likely that they will. Without that option, I have to resort to spamming message boards, Twitter, Facebook, etc manually, in order to drive traffic. I am not opposed to that option, as my site has no way of generating revenue and likely never will... I'm just looking for engagement from readers and ways to generate more readers.
http://www.heise.de/ct/artikel/2-Klicks-fuer-mehr-Datenschut... [german]
I don't give a crud about the analytics of AddThis, and their menu is full of options that most will never use. The key point is sharing for the lazy. The vast majority of Internet users are never going to open their Facebook, write a wall post about something and copy/paste my link in their post. That same person, however, may be really interested in it and be willing to hit a little button that does all that stuff for them. That's all I want. I don't want to jeopardize people's privacy.