way to send a message into the inbox of all members of a Facebook Page ?

From Facebook Help: You can message up to twenty Facebook friends or email addresses at once. However, if you are contacting someone on Facebook you are not friends with via a Facebook message, you can only message him or her individually. Alternatively, if you are an admin of a Facebook group, you can message all the members of your group by going to the group profile and following the "Message All Members" link underneath the group photo. Note that this option is only available for groups with 5,000 people or fewer.

I believe its only limited people not all of your friend because it might be a spam..? :D but you can send messages to your selected friends and have a chat like conversation. :D