Don't really matter if you put your phone number or not cause 2/3 of the people will try to buy it using PM's, I recently put a rifle on Classifieds and got over 10 different PM's asking me all about it , would I take less and etc. instead of picking up the dang phone and calling
However I agree that there should be curtain things filled out in your profile in order to post in Classifieds.
I disagree that since some don't fill in all the blanks then they have something to hide.