Lost contacts on Iphone Sync

I have had the same problem twice on iPhones. I sync to iTunes, and all data on the iPhone is lost. It happened once on my iPhone, and now it has happened on my Wife's IPhone. I am afaid to sync for fear of losing all the precious data entered into the IPhone. What gives??

Same thing just happened to me, why would it overwrite. Synchronize implies no loss of data. I just lost hundreds of business and personal contacts. Is there any way to recover old backups of my phone, instead of just the most recent one?

Well, not only contact list all my songs and video, notes are gone.
This all happened spontaneously, not after syncing or restoring. My iphone was frequently getting stuck, and I had to wait until battery to run out, even to recharge!!!, then the data loss occurred. What I only see is my recent and missed calls, and favorite list and voice mail but only numbers without their assigned contact names.
I tried to sync, my I tunes is not showing my data either.
Now what do I do?

Search for this file AddressBook.data.previous
When you locate it, in the same folder should be another file called AddressBook.data, drag this one from the folder onto desktop
Now reopen AddressBook
Let me know if this helps

this also happened to me yesterday I tried the suggested remedy but no luck I have lost all contacts on my iphone and my laptop are they stored somewhere else on either or can I retrieve them off of my phone???
Help!!!