It is more the use of the domain, than the domain itself. If you are attempting to use a trademarked word/phrase in a similar way or for a similar purpose, you're going to have problems if you're called on it. Owning a domain doesn't automatically entitle you to use in any manner you see fit, and there are so many factors involved that really, one cannot say *definitively* whether you can use a domain for a specific purpose, without looking into current uses, similar uses, existing trademarks, etc.
It is confusing, but basically, you should realize that a domain doesn't equal a trademark (which is why apple.net doesn't automatically belong to Apple Computer, Inc., as apple.com does). If apple.net sold computers, they'd find themselves in trouble (most likely), but if apple.net sells apples or anything besides computers, then they'd have a better time at retaining the name if it were challenged.