Burning Question of the Day: Can men and women just be friends?

So the other day at work, we were discussing whether or not it's possible for men and women to be "just friends", and whether or not those relationships should change once you're married/in a committed relationship. The general consensus was that while most everybody had co-ed "couple" friends, most didn't have any male friends who weren't friends with their husbands first. Most also expressed discomfort at having one-to-one level of intimacy with a friend of the opposite sex during marriage.

I realized later that I was the exception in this situation, being that I do have a few male friends that I was friends with first. While J may know and like them, they were definitely my friends first and still primarily my friends. For example, in college, our dorm was co-ed. And not the usual alternating floors co-ed--my neighbors were boys. Our floor was pretty tight in college, and I had a lot of friends that were both male and female. And I STILL keep in touch with at least one of the male friends (hi Ethan!). And if Ethan were in the area, I'd have no problem meeting him for a meal to catch up. I would invite Justin to come along with us, as I have before, but if Justin couldn't make it, I'd definitely have lunch with Ethan alone. And Justin would WANT me to do just that.

We also have maybe two sets of couple friends (one set is friends that happen to be family), that I'd be okay with either Justin or I being alone with the friend of the opposite sex. For example, Kaitlin, Jesse, Justin, and I usually do things together as a big group when Jesse is here. If we were all meeting at our place for dinner, and we're coming from different places, I'd have no problem with Justin and Kaitlin hanging out at the house together until Jesse and I got there, and visa versa. While Jesse is gone, I'd have no problem with Justin stopping at the house to say hi to Kaitlin if he happened to be in the area.

On the other hand, I have no problem with the member of the opposite sex preferring to wait to come in or come over until their spouse arrives. There have been a few times when Ryan and Renee have met us at our house, again with all of us coming from separate places, and even though Ryan will arrive first, he'll wait in the car until Renee arrives before coming in. And I understand and respect that too. And it doesn't mean that I think we're just "better friends" with Jesse and Kait. Each spousal set has to set those expectations and boundaries for each other based on what works for THEM.

I think for Justin and I both, we trust each other to be in situations with members of the opposite sex that are strictly platonic. Neither one of us has much experience with a significant other cheating on us, so maybe we're a little naive in that way. Though, would I be so easy going about Justin hanging out with an ex-girlfriend? No way José. But in terms of being "just friends", I think the line of concern for both of us would be if we started sharing with or confiding in that person of the opposite sex things that we wouldn't share with our spouse. If that started to occur, then I think we'd definitely need to change our expectations about what sorts of one-on-one situations were okay.

What do YOU think? Can men and women just be friends? Should you have friendships of that nature when you're married or in a committed relationship? What are the boundaries?