The fact that someone may have incorporated under a name or even that they have filed a trademark application does not automatically permit them to use that name. All parties who have legitimate use for a name, share the same rights to a name. Once a name is taken, it's gone. Domain names can be worth thousands and thousands of dollars. The more practical and useful it is for others, the more it will be worth.
Domain names can be worth even more in non-monetary terms.
Companies that have spent a great deal of time and money on establishing a corporate identity may find the value of their domain name immeasurable. The worth of a domain name is high, and there is no limit to just how high. In quick and simple terms, if you've registered the name in good faith, its not a name belonging to an internationally known company, and you can show that you have a legitimate reason to use that name then you are likely to be able to keep that name. One way to avoid trademark disputes would be to choose the right domain name and is similar to choosing the name of your company. You would not want a name that is similar to another company that people cannot distinguish between the two.