If I use a name in my domain of an organization, for example NBA, will I face legal issues in the future? What if I state that it's only a fan site in the footer? Would that be ok? Thanks
Yes. In fact, I owned a couple basketball domains with NBA in them and I got a nice cease and desist letter in a matter of months. Some companies are real aggresive when it comes to these things.
No, you can't do it. A disclaimer isn't going to do anything if your domain name is infringing upon their trademark usage. Some companies will give permission to non-commercial fan sites (no ads or revenue of any kind) but you should get it in writing to be safe.
Now unless you want to start a site for the Nice Bunnies Association then yes, it would be a trademark infringement. As soon as you create a site with content related to the trademark you are likely to have legal issues.
so what about those hundreds of fansites floating here at digitalpoint linkexchanges.buy-sell forums.. All that illegal?
The fan sites usually run into problems by using images they don't have the rights to use. The celebrity doesn't usually own them, it's the photographer who owns the rights and can demand a usage fee they set (copyright infringement). Not all celebrities are going to take action even if it is trademark infringement - some allow true fan sites (no revenue, ads, etc.), some don't care, and then there are the Madonna's who spent vast sums of money (she now owns Madonna.com after proving trademark infringement due to the sites content). There is always a percentage of risk, even if small, that a trademark holder will take action when you try to profit off their name. Having a site that puts them in a "favorable light" does not give you a legal right to use a trademark.