Selection surprises

Given the amount of planning the major sides (England apart) have put into this world cup, I have been surprised by some of the selections for the opening matches. Argentina have their regular full back at fly half (though admittedly he has been known to play there), France have their right wing at full back, as do England. Wales might pick their full back at centre, and have only decided on a captain in the last couple of weeks, as have France. South Africa lost their first choice number 8 and replaced him in the squad with a hooker. The Aussies expect to blood an uncapped fly-half off the bench. The latter strikes me as especially risky, given Steven Larkham's somewhat fragile nature.
Is this a sign that these sides are confused about their direction? Or just a sign that modern rugby is about squads and versatility? Frankly, if any of the coaches of these sides were considering these moves, why weren't they tried sooner? The world cup isn't the time for experimenting. The winners of the last two tournaments had settled teams where every player knew his role.