I can understand on some levels - i.e. you've maxxed out your main character in whatever MMO you play and your groups is in desperate need of a healer, but you're a DPS/Tank class, of which you have too many. So the guild pools money and opens a new account for guild characters - Basically fill-ins, and pays someone to grind for them.
But in something like Starcraft, there's no point. You're signing your own death warrant, and you're lining up to be humiliated by higher skilled players, who will in turn move up because they beat people who are ranked where they are when they shouldn't be, which puts them against tougher opponents, and unbalances the entire system. One person leveling up like this could cause a lot more people to level as he gets beat over and over again and slowly drops back down the ranks, kind of like a shockwave traffic jam. (i.e. one person taps their brakes, and as the brake tapping goes further down the line the time between moving and stopping grows exponentially until it's a full stop)
