One simple case, Anton: Sun vs. Microsoft. MS violated the Eula on the sun engine, so they sued and won. A eula is a contract, and as such, is as enforceable as the laws of the state in under which it is governed allow. Eula's are legally binding in the United States provided they meet the criteria for willing acceptance. They are constantly challenged -- even today, but yes, they are legally binding. Because they are contracts, as well, they are subject to a much wider and more specific body of law than even copyright. Contracts are the secret evil...

thou and I, my friend, can, in the most flunkey world, make, each of us, one non-flunkey, one hero, if we like: that will be two heroes to begin with. (Carlyle)