Finding friends when you are bipolar is very hard, not to mention trying to keep them can be next to impossible. I find that if I tell someone up front I am bipolar, then they distance themselves far from me. They think or assume I'm crazy when that's far from the truth. I have also tried waiting in telling people that I'm bipolar only to have them "dump me" as a friend later. They dump me like a hot potato, like there is something horribly wrong with me. They're either afraid of me or embarrassed by me. And I'm bipolar II which is a much less form than that of bipolar I. People don't think of how cruel and ridiculous they're being, and it's very hurtful.
People with bipolar do tend to think differently from others and can have different emotional responses, but it certainly doesn't mean they're crazy. Bipolar is an illness, it's a brain disorder that causes unusual shifts in mood, energy, activity levels, and the ability to carry out day-to-day tasks. Most people tend to think of psychosis when they think of bipolar, but that's simply not true with bipolar. Bipolar is a mood disorder, you get highs and lows or in my case for instance, as I said, I am bipolar II and I tend to be moderate to low most of the time. To help you understand it more here is a link to a great article on 9 Myths of Bipolar Disorder.