Imagine you joined a club that provided facilities and officials for any team sport you wanted to play with your friends. If you wanted to play baseball, the club had a baseball diamond, complete with professional umpires. If you wanted to play basketball, they gave you a court with professional referees. And everyone always played by the same rules.
One day you go to the club and notice that all the professional umpires and referees are gone. There are still people wearing officials' uniforms, but you recognize them as players you've seen in the club before. Some of them say you can't play on their field anymore, or that if you want to play on their field you have to play by their rules. On their baseball diamond you get four outs, not three before the sides change. On their basketball court, a basket is worth 10 points, not two. And if you want a normal game with normal rules, you have to spend time looking for someone who was running their field that way.
This is the analogy for what Electronic Arts pulled a little over a week ago (and to a point is still pulling today) when official Battlefield 3 servers run by DICE, the studio that develops the Battlefield franchise, began vanishing from Xbox 360 and PlayStation 3 server lists online. Normally, when Battlefield 3 players wanted to get into a game they would select the game mode they wanted and connect to a server automatically. Then Electronic Arts introduced a Custom Servers program that allowed Battlefield 3 console players to rent one of DICE's servers at a rate of $30 for 30 days. Players who rent a Custom Server can administrate their server however they see fit. If they only want to offer a single game mode, they can. They can also choose not to rotate through all the maps. They can also alter some of the basic rules of the game in ways that official console servers never did.
One of the most popular modes in Battlefield 3 is Conquest Mode. Each team has a set number of tickets, which they lose either by respawning players or if they don't hold enough control points on the map. The winner is the team who forces their opponents' ticket count down to zero first. A round of Conquest is played by default at between 200-300 tickets per side, depending on the scenario. It usually takes around 15 minutes to finish one round of Conquest. Now imagine that, with the DICE servers gone, most of the Custom Server owners have chosen to play Conquest mode with a 2000% ticket count in order to make the game last longer. You will see inflated ticket counts like this all the time on player-run servers. What about the player who just wants to play a regular match or two of Conquest and doesn't have a few hours to put into a game of Battlefield 3?
Server stability - a vital quality in online shooters - isn't only about the quality of the internet connection, it's also about the ruleset that's in place. If a Call of Duty player selects Team Deathmatch mode, he knows how the game is going to work. If a Halo player chooses Headhunter mode, she knows what she has to do to win. There may be tweaks due to patches or additional game modes added over time, but by and large the rulesets are stable. That's a reasonable expectation for any online multiplayer shooter game. Competition depends on this kind of stability.