If you are sufficiently experienced to notice something like the URL not matching the official site then you would be indeed be foolish, but I am involved with a group helping people who have no or very little experience of computer use, including emails, and I wouldn't be at all surprised if most of them were to see a message like then they would blindly go through with its instructions - they become a bit dazzled by the fact that they are using a computer and forget about common sense.