As for the matter at hand, I know most people are going to say Hodge here. But they won't do it for the right reasons. They'll go for Hodge because he was unlucky to be dropped in the first place - they'll go for Hodge because he was unlucky to lose his test place - or they might even go for Hodge because he's a Victorian and we have some ridiculously biased members here.
However, the best option for the side, in my mind, is Johnson. Australia's top order has been near invincible so far - so much so that Watson has rarely got a bat. When he has, he's just been required to bash at end and, to his credit, he's done a good job of it - striking at above 100 and not being dismissed. But in all fairness, this role isn't something I'd pick a specialist for, unless they were brilliantly suited to it, which Hodge isn't. Don't get me wrong - Hodge is a gun batsman and I think he'd a do a great job at 4 or 5 in the ODI side if a position came up there for him, and he'd probably do as good a job as Watson batting 7. But there is a better way to utilise this position than smashing a few runs at the end - something which Hogg can probably do nearly as well as Hodge anyway.
Australia's bowling is undisputedly their weak point. They've had massive runs piled upon them recently, and with Lee missing from their attack, it could quite easily go wrong. Watson's good bowling form in this WC - even though he wasn't taking any wickets - has been vital to Australia's success so far IMO. Even though Watson is clearly a batting allrounder, his bowling has been of more use due to the balance of the rest of the side. Johnson himself is an under-rated batsman too - even though he hasn't shown much at ODI level yet due to limited chances, he's gunned it for Qld in FC cricket whenever he's been given the chance averaging over 50 last season, and from all reports, his batting would idealy suit the one day game at #8 because he's adept at rotating the strike. I reckon he's good enough for #8, even if Hogg isn't good enough for #7 - and the awesomeness of the Australian top order more than makes up for that IMO.
Idealy you'd have Watson or Hopes at #7 to, in effect, save Australia's arse either way - but with neither of those players actually available, Australia's relative strengths and weaknesses have to be taken into account. There's no doubt that Hodge deserves the spot more than anyone else, but there's equally no doubt that Johnson would provide more to the team - so he's my pick.
When I first set eyes on this thread, I somehow (though only for a second) got a "R" instead of the "H" and a "i" in between the "ge"... 
