I've had a few people ask me about this. From Carrier Reps, to IT guys, to normal everyday consumers so I thought I'd write a little something about it.

"How did my blackberry delete my address book?"

Well first off from my experience with blackberry I have never seen a blackberry delete its own address book (of course we have seen the blackberry devices clear call logs, and messages due to memory constraint, but that's another story.
It's quite simple to resolve. I usually go to the phonebook (image #1), and press menu>filter (image #2). If there are any of the filters or categories checked and no one in the address book has been set to those categories you won't have any contacts displaying in your address book (image#3-#4). So be sure that you uncheck the categories. (You see I told you that your blackberry just doesn't delete contacts, they are all right there.

Well what if you want to set your contacts up to have filters, how do you do that... well go to the address book, press menu and select either add new contacts/edit contacts (depending on what you want to do create or edit). Once your contacts information has been placed press menu and select categories.(image #5) Select the proper category (personal, business etc) and you are all set. Easy as 1,2,3