Just how erased is "erased"

[InvalidUserID]

Since I got my new iPhone 4, I'm going to try to sell my "old" iPhone 3G.

I did the "reset to factory" or whatever it is that completely erased the phone and now turning it on it goes to the "connect to iTunes" screen.

Is it ready to move to the next person (I've also removed the SIM card).

 

[Applejuiced]

Yes, its good to go.

 

[BrokeMyi]

InvaliduserID,
From my understanding, the content is never actually erased. The location where it is saved is simpley changed to "free space" even thought your old files are still there and will remain there until they are over written. Correct me if i am wrong.