As you know we encourage a lot of customers to get a secondary domain to reserve additional domain names that will refer to their primary domain. Well along with that information we usually suggest using Google Apps for your account to help facilitate user collaboration among your employees. If you signed up prior to 4/27/2011 you're in luck then you have been grandfathered in. But starting from May 10th 2011 on all Google Apps accounts will only have 10 users max for the free accounts and you have to pay to get the business class accounts. I think as of this time the fee is $50 per user per year I think. You get 25gb per user email account storage. You get a ton of space just for email and if you're a business that comes in handy to keep all your emails for reference.
Here is a letter that I received about Google Apps Customers.

Hello,

We recently announced upcoming changes to the maximum number of users for Google Apps. We want to let you know that, as a current customer, the changes will not affect you.
As of May 10, any organization that signs up for a new account will be required to use the paid Google Apps for Business product in order to create more than 10 users. We honor our commitment to all existing customers and will allow you to add more than 10 users to your account for DOMAIN at no additional charge, based on the limit in place when you joined us.
Sincerely,

The Google Apps Team
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