I cannot believe it!?! My XDA (Windows Mobile 6 Device) has had all my contacts, diary etc info wiped by Windows Mobile Device center for the FOURTH time. I just plugged it in and it asked if I wanted to set up a new association (when I had one set up already) - all my contacts had been deleted at this point - BEFORE asking me!! I can resync with my desktop but its a big pain in the butt. I don't know why it is happening?!! How can Micro$oft get it sooo wrong?
I am seriously considering bombing my XDA for an iPhone (once it's got GPS I will).
[update]: There are some registry tweaks that affect related behaviour here.