Ownership - Drawing the Line

A friend of mine recently got married, and shortly after the marriage, he started up a small company (DJ company, if you're interested). Now to my knowledge, his wife has been giving him a hard time, because since they are married, they have shared assets and such, and wants to have her name written in as a company owner for whatever reason.

I don't know how it ended up resolving itself, but where would one draw the line in a relationship as far as who owns what, whether it's a company or personal bits of property. If/when I'm married, I don't really want to "own" her curling iron, per say, but then the house is pretty much shared (even if one may have paid for it or owned it before marriage).

Jam it back in, in the dark.