Microsoft's successor of Windows and Office as we know it
Microsoft has a patented pay-as-you-go system which is currently used not only for Office 365, but also for the Windows Azure platform - http://www.microsoft.com/windowsazure/
There are many sound companies such as NASA, Xerox, T-mobile, Volvo, using Windows Azure and paying for used resources instead of purchasing their own servers. This scheme may indeed prove beneficial for businesses in cases you need the service available 365 days a year, but you will use it infrequently per demand. The idea behind Windows Azure may lead to a new version of Windows, the successor of 7/8, which is just a thin client connecting to the cloud. Users will no longer have their copy of the whole system. This is going to eliminate unauthorized copying because users will never download the software, but rather just control it. The used technology is Citrix. Microsoft and Citrix already have an alliance http://www.microsoft.com/enterprise/partners/citrix.aspx and work together on it.
Once it's all the cloud, you can't even access your own data without paying for it, and frankly who likes having his own CPU capped unless subscribing to some expensive enterprise plan? How easy is it to be the man in the middle in case of a cloud?