'Two-factor authentication' may  satisfy the security concerns of many CIOs but it adds a burden to users.

Google's Enterprise blog announced that some customers would soon have the ability to add two-factor authentication to their Apps accounts.  This service is now available for government and premier customers and will  roll out to all Apps users and Gmail users in the coming months.

It is an opt-in service. Users identify their home computers  only once for authentication.  Company Apps administrators may not be as lax, however.  Once enabled by an administrator, end users can set up the security feature in the accounts tab in Gmail settings.

Google explains: More