Writers who work together amaze me. I have no idea how they do it. Last year at Saints and Sinners, I asked Timothy Lambert and BeckyCochrane lot of questions about how they work together. Poor dears. It probably felt like an interrogation. But talk about gracious! I learned at lot from them.
I also pepper Chris Owen and Jodi Payne with questions from time to time. (Look out Myc and Shanye - you may be next!)
The closest I've ever come is working on an anthology Beth Wylde is editing for Phaze. She gave us the setting and a couple main characters and let several writers run with it. I had a somewhat similar idea last year for an anthology and even pitched it and got it accepted, but had to drop it (with the blessing of my publisher, thank goodness) for my YA novel.
So I'm fascinated by people who can co-write, but didn't think I'd ever seriously consider it. But... it's too early to talk about anything, because we're still brainstorming like crazy about what kind of project we might possibly do if we can get it together, but Helen Madden has been a friend for years now, and we come up with eerily similar stories from time to time. I can't remember the title of her story (she'll hopefully post it in my comments) about a man who meets a Goddess at a bar at the end of the universe, but I remember reading it on the Erotica Readers and Writers Association Story Time list at the same time I was working on She Comes Stars. I swear we didn't talk about it beforehand, but as soon as I read hers, I thought "She's going to hate me forever because it looks as if I'm ripping off her idea." Luckily, she didn't hate me forever, but ever since then, when I get hit by a great story idea, I run through her stories and make sure she didn't get there first. She usually does. Her novel Demon By Day and my novel Chaos Magic have some elements common. (They're both great reads, for one.)
Even if it never amounts to anything, this creative conversation between us is spawning plot bunnies like a tribble on shore leave. For every one she lobs over to me, I'm sending a couple back. Result? I'm up to my knees in killer plot bunnies of doom.