Blizzard Has This To Say About Private Servers
“ …you may not host or provide matchmaking services for any of our games or emulate or redirect the communication protocols used by Blizzard Entertainment® in the network feature of its games, through protocol emulation, tunneling, modifying or adding components to the game(s), use of a utility program or any other techniques now known or hereafter developed, for any purpose including, but not limited to network play over the Internet, network play utilizing commercial or non-commercial gaming networks or as part of content aggregation networks without the prior written consent of Blizzard Entertainment. ”
The Private Servers Carry Have This To Say About Blizzard
“No one from Blizzard, associated with Blizzard or any such affiliated company or anyone directed by Blizzard or its Related companies is permitted to enter these web sites or view any content contained within these sites at any time what so ever due to controversial reasons.”
These “controversial reasons” are whether or not this is legal.
At the moment, the only action Blizzard can take/has taken against users of Private Servers is to ban the accounts they may hold on the official Blizzard servers.
The Allure of the Private Server
There are many different reasons people go to Private Servers. Some may to it for an “instant 70”, some may do it for “GM gear”, but I think most will do it either so they don't have to spend the money, or because their parents refuse to fork out the month payment.
The Disadvantages of the Private Server
Very few/no servers are actually truly “blizzlike” (identical in behaviour and XP/drop rates to the official servers). This is a problem for the majority of people who's parents won't make the credit card payment/want to play the game seriously.
Also, many of the Private Servers are unreliable, laggy and have frequent downtime.
Some people also consider using a Private Server to be “morally wrong”, just another form of stealing. The Servers claim that they aren't selling the product, so it's fine.
The Options
There are actually other choices to buying the game disks and playing on a private server.
You can save up for the disks, or get them for a birthday, and then go to Target every 60 days to buy a new game card. This has the advantages of the guilt factor being removed, AND allowing you to play properly, as the game was meant to be played. Oh, and it's DEFINITELY legal.
If your pocket money can't cover the $15 a month, tell your parents that you're willing to clear the table/sweep the floor/stack the dishwasher/wash the dishes/clean the car/water the flowers for $1 a day. The subscription to WoW costs about 50 cents a day, so you'll be able to afford the membership costs quite easily! Odds are, your parents will be THRILLED that you're saving for something properly.
In the end, though, how you play is your choice, and it's you that deals with whatever consequences.