YoVille will NEVER ask for your password, so please be wary of malicious emails and/or forum posts that request your password, including via web links.
I remember that there was a setting that made it so only buddies can send you gifts. I can't seem to find it anymore, is it attached to another setting?
I occasionally will go wishlist or other gifting events and give items to people who seem to be genuine. I don't want to take other's things because there are other players there that could use them more.