I tried dating two people at the same time (ie: having open relationships as opposed to just fucking around) because I thought it would help me deal better with jealousy. Forcing myself to walk through the fire was not the best therapy for me. It actually put up a barrier to further intimacy and made me assume that I could never expect total committment from anybody.
What I quickly learned was that I was compromising what I really wanted. The social enviornment I was in at the time really fostered this kind of experimentation and I look back at it now as an educated mistake.
I admire people who can form safe, loving bonds with multiple partners but I feel it is a rare thing for people to manage and contains more risk than it's worth.
Just my .02. Looking forward to hearing others' stories.