To be fair, I had that experience with my first iPod. As soon as I got it, I synced it with my computer and loaded up a ton of songs on it. This took a while.

Some time later, I connected it to my dad's computer to put a couple more songs on it. The first thing it did when I hit "sync" was delete everything on the iPod.

I learned that day that "sync" meant something different to Apple than it did to me.

I'm sure it gave me some kind of prompt but it was not a clear "hey this is going to delete everything" prompt.