There is a stigma attached to bisexual peoeple being confused and/or greedy.
But I've observed bisexuals often tend to me more on the 'liberal' slide, which isn't the same as being indiscriminately promiscuous or oblivious to the feelings of their partner. There are plenty of bisexuals who will only date one person at a time but there are also plenty who feel the need to date one person of each gender.
I myself am genuinely polyamorous. I know it is dangerous to make that known because people tend to see polyamory as an excuse to sleep with whoever you like. I've only been actively dating for a year but genuinely fall in love with more than one person at a time. I don't like the idea of dumping and 'swapping' people. I don't get 'bored' of partners or look for things one person can give me in another. Like girls asking who they should 'choose' on yahoo answers and being told to go for the one with money. If you really love someone, you love them, and it never goes away. If they are genuinely detrimental to your wellbeing there are other sorts of ground for a breakup besides throwing what you have away simply because you love someone else, too. Love is too precious to just throw away or treat lovers like a pair of shoes.
Anyway, my boyfriend knows this and I'd really like us to share a girlfriend if I ever meet a special girl. It'd be selfish to expect to have a second partner of a different gender then get all jealous if he looked at her.
It's a bit different with girls I guess. Most guys would seemingly jump at the chance to date a girl who likes to frolic with other women, though they may feel jealous if romantic feeling and time-sharing are involved. You see there is an emotional aspect to consider, not just the sexual one...
A menage a trois of sorts would suit me wonderfully, but only with people who really mean something to me. That I have a deep love and care for.
I might have gone a bit off-topic but thee are polyamorous and monogamous bisexuals and sluts who don't care who or where they get their kicks from. There is a distinction lol.