There's nothing wrong with an individual person labeling themself "bi-curious" if they so desire, but the word has a history of biphobia (and homophobia) because of the whole "it's just a phase" implication. It'd be great if we could move on from the If It's You, It's Okay and But Not Too Bi tropes, thanks.
I think one good thing about the bisexual romance options in Bioware games is that they don't rely too heavily on this trope:
Silk Fox - bisexual (preference for males?)
Sky - "bicurious"
Liara - bisexual (stupid *monogendered* caveat)
Leliana - bisexual (preference for females?)
Zevran - bisexual (preference for females)
Isabela - bisexual (preference for females?)
Anders - bisexual (pansexual?)
Fenris - bisexual (preference for females?)
Merrill - bisexual (slightly ambiguous)
Kaidan - bisexual (preference for females; possibly bicurious?)
Kelly - pansexual
Allers - ugh.......
I think the only bisexual option who would definitely fall into this trope is Sky. I could see an argument for Kaidan as well. In general, there seems to be a trend towards preferences for females regardless of the LI's gender, I think. But I might be wrong because I haven't romanced most of these ladies, so I'm going off of what people have said here.
ETA: I never played NWN really, but apparently Kaidala (from one of the expansions) was a bisexual romance. Any thoughts on her?