ughaibu: there is another bad effect, imagine someone is playing with the weakest (regarding to rating) account in that chain, then its rather unfair, because he can be playing a 2400 instead of 1500.
joking is an interesting exception, because usually weak players use this and he is quite good, he would gain top 10 rank using his normal play, just it would take a bit longer time.
But people should learn to be patient rather than cheat :) If a good player who would also belong to top 10 would constantly play against "the weakest in the chain", he would get there much harder. If he would see that player as marked a cheater, he can choose whether he want to challenge the main account of the cheater, whether he doesnt want to play cheaters at all, or whether he just loves the game and doesnt bother about ratings so he plays the weakest in the chain and is happy