Player servers keep game alive
Not really they take income away from the developers since players can play the private shards without paying for official accounts. This hurts the developers and makes it less likely the developers will continue to work on the game or develop a sequal. Should the developers stop running the official server then its another matter altogether but while the official one is still up it takes business away from them.
Congratulations! You've completely mis-interperated my post! Here's your grand prize ...
But all on the serious side, what I meant for your mind to come across is that private servers keep the game alive socially. It doesn't matter if it's ran by Satan himself, it's still World of Wacraft ... so it doesn't matter if the servers belong to Blizzard Entertainment or not. Private servers are there for the players whom don't like an update or patch and prefer an alternate way of playing ... thus creating the name "player servers". Now if you meant that "private servers KILL the game server's population" then you've got a point.
Who actually reads those anyways? I'm getting bored just reading a fraction of the sentence you've supplied me with off of the Terms of Service. *yawn*