My friend Becky makes the case that, rather than pooling all their money, it's a good idea for couples to pool some of their money, and leave the rest separate--the idea being, more or less, that the money that's together will help avoid the conflicts that come from having all your money separate, and the money that's separate will avoid the conflicts that come from all your money together.
I really feel that the opposite is true--keeping some money together and some money separate opens up the door for both types of problems.
I'm reminded of a buddy of mine who was a missionary. Normally, missionaries serving together keep their finances separate, for the only real good reason to do so: They're going to be leaving each other eventually, and it will make the separation easier.
However, one missionary he was living with convinced him it would be a good idea to pool part of their money for food and other expenses.
What do you think happened? The other missionary ate all the food, even though they'd gone in halvsies on it. The other missionary spent all his personal money at the start of the month, so when unexpected expenses came up my friend had to pay for all of them. At the time I met him, this missionary had a bunch of "rainy day" money saved. When I saw him again after he served with this guy, that was entirely gone.
Same thing in a relationship. Let's say Marci and I did this. What I got in an accident, and I had to use Marci's car? Would I then pay for the gas and oil changes for Marci's car, since I'm the one using it? But I still have to pay for the deductible for my car.
And what about when we're doing something together that only one of us wants to do? If we go to a comic book convention on my day, would I pay for both of us, since I'm the only one who really likes that? And if we go see a chick flick on her day, should she pay, since it's a movie she wants to see?
The problem with the above examples is how independent they both try to be. My car. Her car. My night. Her night. If we really are in this together, that's our car. It's our night. It's the separatedness that makes conflict inherent in each of the interactions above.
A couple of points--
First, I am not saying multiple checking accounts are a bad idea. I'm going to be opening up another account here eventually, when the first check for ad revenue for this site comes in. What promotes conflict is separate checking accounts--accounts where expenses are, in effect, "hidden" from the partner.
Also, I'm not saying complete unification of finances is going to be conflict free. I'm saying that pooling all the money creates a sense of unity with both partners that makes the conflicts easier to handle. Even if my wife and I are at odds about whether me buying printer toner is more important than her buying a sewing machine part because we don't have the money for both, the fact that we're arguing about our money and what's best for us puts us a step ahead of those couples who are arguing about "my" and "yours" and "you" and "I."
And because we've taken that attitude about everything--even our debt--that puts us at a full advantage. She came into the marriage with a lot of debt, and a lot of conflict came from her continuing to think of that debt as "hers." She didn't feel I should have to pay it. Now, by fully relinquishing "her" debt to "us," we're able to pay it off a lot more effectively than if we were still fretting about whose was whose. The second we decided to become an "us," the debt had to, had to, become "ours."
Would it have made sense, financially, if I was investing "my" extra money and getting a 10% return, while "her" debt was still costing 18% a year? It might have made sense for me, but it wouldn't have made sense for us.
I'm not saying we won't eventually budget each other a few dollars. We aren't doing that right now, because we're paying down debt so aggressively--right now the sewing machine is still broken and the printer still has no toner--but we'll eventually reach a point where we can budget out for a few of our "own" purchases.
I am saying that since money is directly linked to emotion, fully "investing" in a relationship by contributing your entire salary allows and creates a more complete emotional commitment. Failing to fully commit financially may represent that a person hasn't fully committed emotionally.
And, since partners know this too, a complete surrendering of one's finances to the relationship will be perceived as one of those actions that speak so loud it's hard to hear what you're saying. So will failing to make that commitment.
So again--I'm not saying completely pooling finances will eliminate all conflicts. It won't. I can testify to that.
I am saying it can create a sense of relationship security, of unity, that cannot be had otherwise.