I wish the critics would just come down to say it, but many of them don't: "I don't want another player being either able to kill me faster because of something they bought in the cash Cabal Alz shop, or a player to be able to buy something I "worked" hard on to get." That's fine, just spit it out.
But if we are talking about advantages here, and mainly financial ones, my point is that players have been using money to gain actual advantages since it was OK for a player to stay up for 4 days camping something.
There is no more noble way to spend your cash, or a way that is more or less "cheat." That doesn't apply because not only are there no official goals (meaning forced by the game) in most MMO's (look at how much success that brought to Fury) but even within games that have many popular activities, there are ways to play outside of those activities.
Let's not let this argument be about "one player is spending money to gain an advantage.." as though cash shops are the great enabler, allowing the sneaks and the lazy to suddenly bask in the glory that the "hard working" bask in.