Here is a Way to Select all our Friends on Facebook :
I Tried this Method on Mozilla Firefox and Chrome Browser and it worked on Both.1. Download And Install Greasemonkey Plugin For Mozilla Firefox Web Brower.
2. After Installing GreaseMonkey Plugin, Install Select All Facebook Friends Greasemonkey Script ( If You are Using Google Chrome 4.0+ Then you can directly install greasemonkey script without downloading the above plugin )
3. Now Go to Any Facebook Fan page or group after installing the script and you will see something like this screenshot :-
You Will Notice Start and End. Now you need to enter the number in this field to select all your Facebook friends and as you can see i have entered 0 to 585 and after that click on “Select Friends” and this will select all your Facebook friends according to the number which you have set in Start and End. Now Click on Send Invitations to Invite All your Facebook friends.