Your birthdate alone is something like 14 bits of information. I've never understood why some ask for it, and always tend to just make sure my age shows up as a

Your birthdate alone is something like 14 bits of information. I've never understood why some ask for it, and always tend to just make sure my age shows up as at least 18. And I would never put my zip code on anything purportedly anonymous. I bet if you collected statistics on internet users, you'd find out a lot of people were born on January 1. 1980.