I don't understand the down votes against megablast. He has a point, one that you might not agree with, but that does not necessitate a down vote.
That said, I do agree with this point of view. If he really wants to jump out of Microsoft into a startup and it would make his wife feel uneasy, its better to have that talk, explain why he wants to make the jump, and hopefully get her support.
He actually writes the opposite, he is assuming he is leaving microsoft because of an agreement between him and his wife:
> so you are just going to quit working at Microsoft because of some agreement you made with your wife.
Besides that, there would be something to be said for the opposite argument, but the way I read the OP he has made a deal with his wife that said "Ok, I'll work for 'the man' for 5 years to give us stability, but after that I'll want a change of scene, and more risk", and she said "ok, that's fine with me". Now they're approaching the end of the 5 year period and he's checking out to see what his options are.
The biggest single risk in stepping down from a behemoth like microsoft to a much smaller company is that you can't rely on other people to do the mundane stuff for you (so that means you have to provision your own machine, set up your desk and so on), you are expected to self-motivate and work unsupervised for longer stretches. There is a big cultural difference and people working for large companies can get institutionalized to some extent.
But judging by the OPs responses that is not the case with him. Not by far, he seems to have his stuff together pretty good.
That said, I do agree with this point of view. If he really wants to jump out of Microsoft into a startup and it would make his wife feel uneasy, its better to have that talk, explain why he wants to make the jump, and hopefully get her support.