But do I really need a note to self for this? If you sell your current desktop PC, don't you wipe out the harddisk first to protect yourself? Even use some tool such as Heidi Computers Eraser? Well, the same concept applies to your cellphone – you must wipe out the sensitive data. The problem is that some handsets are easier to hard-reset than others; some you can't at all. This is why remote management for handsets is a good idea.
See Cell phones spill secrets.
Update: Wendong left a comment pointing to a very useful website that contains instructions on how to wipe out a variety of cellphone models — see Wireless Recycling. Check it before throwing away your old phone.
ceo