Introduction:

In this series, I will write about some aspects of the platform geared specifically for  new developers based on talks I gave on Force.com. Lets start with the way you sign up and get your developer account and what you should keep in mind before you choose a username.  

Your Username, your Identity and your Orgs: 

When new users create a login and get their developer edition orgs, they
are asked the following pieces of information which are crucial: 

Email and Username.

Their first encounter is like this: 

Note that the helper indicates that the username and the email addresses do not have to be the same.

Unfortunately, a lot of new comers to the platform use the same email and username.  Perhaps it is not clear why you would like to keep them separate. If you will be using Force.com platform for some time, you may be trying out different versions and new features as you go along. Thus, keeping them separate is necessary. 

Here is what happens.

After you sign up, you are allocated an "org" and you have administrator privileges.

An org is a virtual container of applications and can also host sites. An application is a series of tabs, which comprise of objects or virtual pages. An org contains a set of users and allows them access to the applications via a set of user profiles. Thus, a users profile is a key aspect of who (s)he is in an org and what (s)he can do or see, whether it is accessing a subset of applications, its metadata, owning data, CRUD, participating workflows, etc. Consequently, the user's profile dictates the participation of all things that an org has to offer. A user who has system administrator profile has the ultimate power in an org.

Each user is identified by an username which is the form of an email. However, this representation is just a unique identifier,  i.e. it could have been a URI for all matter of practical purposes. The username although has the form of an email, is not really a "valid email address". It can be a fictitious name for that matter as long as it is syntactically correct. Thus, the username only relates a person to a specific org and ties the user's identity to an organization.

In other words:

• The username is uniquely tied to the org.
• The email is the vehicle how a actual user is communicated with.

Pictorially speaking:

Thus, a person may be related to multiple orgs at the same time with different username/passwords while retaining the same email address. This provides a lot of flexibility. The usernames are related to different orgs, but you continue to retain your email address. A user can participate multiple orgs via different usernames but happily retain his/her email address.

Who am I?

When you are creating a new developer edition user, you are basically 

• Creating a new org
• Creating a unique user that is identified with the username
• Assigning the user to be administrator for the newly created org. 

Therefore, be careful with this binding as your chosen unique username will relates you to an org.

In order to play with different versions of the platform, it is highly recommended that you choose a username different than your email address from the get go. As you sign up for new editions, prereleases later on, this approach allows you to be flexible. This is possible if the first time you signed up your username and your email were different. This will allow you to associate different usernames with different orgs, while retaining your real mailbox and point of contact.