I am not very good in tracking birthdays of friends, there always manybirthdays in spring. Addtionally skype notifies you when one of your contacts has birthday. Very handy but is it correct? Do I want that? Did I ask skype to tell everybody it s my birthday? Hmm … do I have to respond to a note because I know that he knows that I know …
I decided run an experiment. Since 5 days it s my birthday every day on skype. I got some messages, comments, emails and even phone calls. Some people were doubting, some noticed on the 3rd day. It was fun.

“Skype is a snitch.” Marius posted in a comment, very true.
(Btw, my birthday is on 27.12.)