There's also the doctrine of laches (I'm not a lawyer, but I have managed to absorb some of their terminology) which holds that if you've been doing something with the knowledge of the trademark owner for long enough, they can't suddenly start objecting to it. This wouldn't apply if you made a major change to the nature of your use of the name, however, as they could then sue you about your new usage -- for instance, if you passively held the domain name for long enough, maybe they'd be barred from suing you strictly for passive holding, but if you then started using it for an active web site they'd have a new claim; or, if you used it for years to run a noncommercial fan or protest site without objection, then turned it into a site selling competing products.