No. When you have a registered trademark, you do not (contrary to what you might believe if you read most Internet forums) "own" the word; you have only registered your usage of the word in a specific field, which allows you to make it easier to prove in court that someone else is being confusingly similar to you in their conduct of business.

However, for most people, their business is small and focussed, so usages of the same name in other fields would not be defendable against someone using it for adult entertainment production. This would be exceptionally difficult an acronym such as "npr", especially as it has been used for many things in the past (such as Northern Pacific Railroad, although Nevada Public Radio is a more interesting example).

(edit: After posting this I noticed I had had the tab open long enough that some other people responded with similar commentary, but I'm going to leave this up as I think it has a slightly different character, as well as a funny example.)

Probably not. Trademarks are specific to a particular market or kind of product. For example, Apple Computer didn't really conflict with the Apple Records until Apple started selling music. So a porn company probably wouldn't legally conflict with your trademark.

What? There's a whole huge controversial process around trademark disputes for TLDs, spanning all the TLDs, .XXX included. It was all Slashdot could talk about for months and months, because it favors trademark holders.

It's also possible to "tarnish" a brand. So if you register something like Disney.xxx, they might be able to sue you on those grounds. There's also increased protection for famous marks, And finally, there are some marks, like the Olympics & Red Cross that are statutory trademarks. That is, they were created by international treaty and have special rights associated with them due to the legislation that enacted the treaties.

In short, it's more complex than that. IANAL, but I sure wouldn't go tempting lawyers by registering apple.xxx or whatever.

Even if you can, it will take time, waste energy, leave uncertainty, and only the lawyers benefit. The fee people are forced to pay is an insurance policy to prevent all that hassle.

Does that cost more or less than 80 USD/year or whatever it is?