During a registration process what would the reasons be for using: username/password or email/password combinations to register the user?


Is it a case of identification once in the system (may be preferable
to refer to a user by their username instead of their email)
Simplicity - using email means the user dont have to create two
memorable items?


What other reasons are there for choosing either option? Is there a relationship between the type of service? 


Question: How does owning a home and paying on a mortgage fit into family savings and investment?
Answer: Have you ever tried adding up all your mortgage payments over the years? That sum, plus all the money that you put as a down payment (including various fees
paid at closing) plus all the repair and maintenance work etc) is the amount that you have "invested" in your house. (Yes, you can account for mortgage interest
deductions if you like to lower the total a bit).  Do you still feel that 
you made a good "investment"?