Whenever I read a User Story, my first question is "Really?" I put myself in the role of the User and ask "Do I REALLY want that feature". Security is one of those areas where User Stories are often written from the perspective of the user of a system but, as others have pointed out, they don't want to have to login, or create complex passwords. They just want to get to their stuff and have their stuff protected.
As well as asking the "Really?" question, I look to see if the User Story demands a particular solution. Security is, once again, a great example. Most User Stories do seem to insist on requiring passwords. But why? I like to write User Stories such that I give the developers room to consider alternatives. By doing this, we create an environment that encourages innovation. A good thing.
So, here's what I'd like to see:
As a New Member
I want to create an account quickly and easily
So that I can access Member Benefits
As a Current Member
I want my personal information kept private
So that I can maintain my privacy
Finally, if the "As a ... I want ... So that ..." template isn't helping you, feel free to use something else but I'd advise that you understand the reasons why (and "It's too difficult" is probably not the best answer :)