I have a client with no physical offices, where most of the users work from rented offices (by the hour), their own homes or on the road on laptops. The users (about 20) are roughly evenly distributed between Europe, North America, East Asia and Australia.
The client needs to deploy Active Directory initially to support SharePoint and Team Foundation Server, and would need to be secure and highly available.
One solution I have considered would be to use Amazon EC2 on a VPC private subnet, and have users join the domain via VPN, or a similar solution on Rackspace, but adding adequate firewalling or VPN. Are there any other solutions I should be considering, possibly non-cloud based?