How should I prep a laptop for a return? I'm returning a Macbook Air I purchased last week at an Apple Store (not because I don't like it, I just need a bit more screen real estate) and I want to make sure I put it in an acceptable state. I'd like to remove all the data that I've put on it in the last week but I don't want to go overboard.

Should I format the drive and return it with no OS? Format and reinstall the OS? Leave it as-is and trust Apple refurb to not look at my data?
If you're pressed for time, and since you mentioned the Macbook Air was new and purchased last week, it probably was installed with OS X Lion which has full-disk encryption. If this assumption is true, then


Back up your data. I'd recommend using Time Machine (so you don't
have to re-setup your user id, install apps, etc).
create another "throwaway" admin id, and log in to your "throwaway"
admin id
and delete yourself from the Mac using System Preferences -> Users &amp; Groups preference pane.