I wrote a plugin for dealing with logins a few years ago at a company I worked for. One thing I had was the ability of an admin account to login as another user so you could see that users views and manage their accounts. Perhaps I should have used a standard rails plugin, but I wasn't sure how to accomplish the same thing that way and would have had to figure out the inns and outs of the plugin. I had to write my own code, but if I needed to make changes to do various odd things in the future I was somewhat more familiar with the plugin. It also got me to get a feel for how to write a plugin so it seemed like a good thing for me in a way, yet I still suspect some people may think it's not such a good thing to write your own authentication (although alot of rails books have examples of sessions and so on with login etc)
I need to revisit this however as I am not sure if I mention it in a job interview if it would be considered a plus that I wrote a plugin or a negative that I didn't use one of the standard ones.
