I think in all of the talk about Hillary, there's been one simple obvious explanation that's been overlooked.
Naming Hillary to Secretary of State makes some sense - she does have real qualifications, true. But the same could also be said for Attorney General and or Secretary of Health and Human Services. My best guess is that this is The Deal. This was the price Hillary put on her unconditional support for the general election - she gets to be the first person offered a cabinet position, and it's one of the Big 4. Honestly, I think that's a fair price, really. If I'm right, in practical terms it came down to State or Justice - Hillary doesn't have the technical background for Treasury or Defense. The problem with any cabinet post for Hillary is this unique, multi-dimensional boat anchor she's married to. Interestingly, any and all concerns regarding Bill are probably magnified at State compared to the 2 most plausible alternatives (Justice and Health and Human Services)
The Clinton Foundation has been much discussed, but it may be the smallest real concern It's possible something genuinely problematic turns up in the vetting process about President Clinton's foundation. He has always been willing and able to skate extremely close to the ethical edge. It's a consequence of his character that, frankly, prevented a good President from being a near-great one. It created one opening after another for his political enemies to attack and kept his political allies on the permanent defensive. Eight years as President didn't change that, eight years out of office sure as hell won't. But Clinton always went right up to the edge, never quite truly over it, the way, say, Dick Cheney does. So forget that for the time being.
There are 2 other concerns about Bill, though. One is high politics and the other is low farce. Which would rather hear about first? Yeah, I thought so. We're still doing the politics first.
As a matter of high politics, William Jefferson Clinton is an ex-President of the United States. While no longer in office, his word and opinion can, properly used, carry weight and meaning in world affairs. Jimmy Carter is the preeminent example of how this can be done right. Ex-Presidents are very useful folks in international relations. They are the guys you send when you want to send a public, not private signal, that you care, but not to the point of official action, about some matter of interest. But that is partly precisely because ex-President's can't be given diplomatic instructions, marching orders, or hell, even talking points they're likely to pay attention to. However, the role of the spouse of the Secretary of State of the United States is basically twofold: 1)Be gracious at diplomatic receptions, parties, etc as required. 2)Make no news whatsoever. Bill can handle 1. 2 is flat impossible for the man, both by his own nature and his position as ex-President. This will enormously complicate Hillary's job as Secretary.
As a slightly trivial matter, there's also the protocol matter of an ex-head of state being the spouse of a minister. In diplomatic protocol there's a well-established pecking order and protocol for head of state, head of government, and government minister with corresponding protocol for ex- all of those. I'm not sure that Bill being an Ex-head of both state and government doesn't create some technical headaches in this area.
So that's the high politics. The low farce...Bill Clinton was willing to publicly humiliate his wife when he was governor and President both by chasing, well, pretty much anything with a pussy and two legs. Rumors are that behavior hasn't changed, either. It's Hillary's lot and choice in life to choose to put up with that or not. At the end of the day, she knows what her husband is like and her call what to do about it. But now the shoe will be on the other foot - now, Hillary will be the public face of the United States representing us to the world, and Bill is her private citizen spouse. Bill chasing after free poontang now - and getting caught - is public mortification to our Secretary of State, and possibly a diplomatic incident. Is Bill ready - is Bill even able - to keep it in his pants for 4 to 8 years?