One advantage of publicly disclosing information about gender is that you know it's public. It's possible to glean someone's gender from the language they use (see
http://bookblog.net/gender/genie.php), meaning people who kept their gender private may be lulled into a false sense of security. Admittedly I still agree that you should always have to option to select which of your details to make public (or to limit which groups/circles this information is available to), but thought I'd chuck in a counter argument to keep things interesting.
