If you are looking for a place to share your travel photos and stories, then try BigRoom.
Technically, the database administrator has the ability to know the exact username by making a database query (I believe all other sites which have the similar feature are the same, as long as you can manage your anonymous posts under your account). The "anonymous" mode is an option for people who wants to hide his/her username from the public on a specific question.
I think maybe I'll change the label of this option to "Hide my username", which would be a better name. :D
Anonymous questions are meant to keep the privacy of a user. To keep everybody from knowing who they are in case if someone they know run into their profile and see all these questions/answers. Only those authorized of this site should have the privilege to know who it is.