Multiple Profiles using firefox

Ever faced this situation, you are logged into your gmail, yahoo, orkut, hotmail etc. One of your friends came up to you and want to check his/her gmail,yahoo,orkut etc. You need to log out, I know its quite irritating. But thats where multiple profile feature of firefox come to rescue, you can use following command.

firefox -no-remote -p

create a new profile for your friend and you don't need to logout.
This is also useful when you are developing web application and need to loging as multiple users to complete one usecase. I generally update my desktop firefox shortcut with above.