My wife and I have seperate accounts (checking, savings, IRAs, stocks, etc), but we do the budget together for the most part. It's more of an adminstrative thing than security. Our accounts are tied together so we can pass money back and forth but we don't see the balances. Because I spent the last two years paying down every cent of debt (except her student loans) there isn't much strain on our financial life so it works. I guess if we were scraping by to buy food and I kept showing up with new tools or more hockey gear it'd be a problem, but we have a pretty healthy buffer/savings which goes a long way.
We divide up the bills as well. I make 2x more, so I pay for the rent, DirecTV, and cell phones. She pays her student loans, electric, utilities, and 'her' stuff like her New York & Company card. Again, mostly administrative. I feel like if we tossed all our money in one big pot and paid out of it that way it'd create more ill feelings than what we do now. If either of us runs short, the other helps out without an issue. Hell, even at Christmas we divide the Christmas gift list and keep them seperate.
Seperate is just easier, I think it eases tension rather than creates it. If were checking her NY&C statements she'd feel more self-conscious in the store and not have as good of a time. If she was checking my Visa statement I'd be defensive about all the dumb **** I buy on Amazon. So long as we're financially healthy as a unit (see business analogy above) a little bit of independence goes a long way.
Bottom line, seperate accounts have their place in some relationships and are not a steadfast indicator of distrust.