I have a domain (and a website) that is closely related to the very very well known product. If that product was name Foo, my domain is foofaq.com and provides faq and news about Foo.
At the beginning, the Foo was brand new product and they liked that people write about them. I was in direct contact with one of their official representatives and they were even doing moderation of comments on my website! They started that contact and they offered me cooperation. I have all emails preserved, and all comments they done on my site are still there.
After some time, they become huge and they got bought by some other company (hundreds of millions $). Foo is still on market, working well but now they want me to shut down my website so that end users do not confuse thinking that my foofaq.com is an official website.
So the question is: Can they just change their mind like that?