Say I see a very popular site (gamewinners.com) and I register a domain winnersgame.com and it's about gaming would that be considered infringement?
Yeah there would be no problems AFAIK, the only thing though is that it will probably stay in the same niche. And many people that visit your site, might think it's a new version from the other one and on their next visit go to the other site again
Imagine for a stupid example, DigitalPoint is popular but if there was a new awesome forum PointDigital there is a big chance I never get back to that because I know the words DigitalPoint way much better & longer than the other one.
Ofcourse this was a bad example