FTA: "WARNING: Using the trick above to subscribe to TechNet Plus without participating in the research activities is in fact illegal, and the subscription may be revoked and made inactive anytime (proof from 1/1/1900 expiration date)."
I don't know about illegal, but it might very well violate their terms of service, etc.
I don't know about illegal, but it might very well violate their terms of service, etc.