This is the notice on their TechNet site (http://technet.microsoft.com/en-us/subscriptions/ms772428):
Beginning in mid-March 2012, subscribers to TechNet Subscriptions (excluding TechNet Standard which are entitled to 2 keys per product) may access a maximum allocation of three (3) product keys for Microsoft Office and Windows Client products in connection with their subscription. The allotted keys may only be used for software evaluation purposes. Once the maximum keys have been activated, no more keys will be made available. Additional product keys may be acquired through the purchase of an additional subscription.
This is another example of where Microsoft is digging away at their partner base - they can reduce the usefulness of these programs only so far. This limit was originally 10 installs, and if you happened to exceed through valid testing, you called and they'd activate for you. Then in September 2010 this was reduced to 5 total activations. Now it is being reduced to 3.
How many people can completely test a number of full deployment scenarios with a grand total of 3 activations of each product? Or, put another way, why is Microsoft charging their partners more and more money for them to test scenarios where they are trying to deploy Microsoft product suites?
There's more on this topic over here: http://www.zdnet.com/blog/bott/microsoft-slashes-product-key-allowances-for-technet-subscribers/4644
The Outspoken Wookie