I may be posting this because my current views on WotC aren't all they could be, that said, this is exactly the sort of thing that results in layoffs because you don't sell enough games.
If you have fans so happy with your product that they'll create internet sites advertising it (or giving away free versions, free samples are GOOD!), you're on the right track. Sending cease and disist notes to those customers...no so much.
If a site is so bad that it's threatening your copyright, you find a way to work out a licence with the fan. Seriously, is there any chance Hasbro is going to lose their rights to RISK?
YOU GO OUT OF YOUR WAY TO HELP THAT FAN CONTINUE SUPPORTING YOUR PRODUCTS.
Pay them if you have to.
In case your wondering, when I rule the gaming world, if you create a site that allows people to play my game for free, I will insist you provide large, obvious links to my site that say "If you like this game, click here to buy it."