What are your experiences on telling other people of your disease? How do people react? To whom have you told?

I was diagnosed with bipolar a couple of years ago, although have had it my whole life so the people I knew already were used to me being a bit off the track every once in awhile. First it took almost a year before I accepted it myself, then I told my closest friends one by one. Of my family only one of my two sisters and my Mom knows.

My problem at the moment has to do with the fact that I am 34 and single and at least in this remote corner of the world it translates into searching a partner for life. With every guy I start dating there is the same question: what are my responsibilities in telling of the disorder? at what point should I tell? how much should I tell?
I don't want the relationship to go too far before telling so I don't get too attached myself (which is usually in a couple of weeks) in case the guy freaks out, and on the other hand I don't want the guy to know if it is not necessary - in the case we break up. My relationships tend to last a few months. So am I obligated to tell at all? If I tell after a few months when the relationship seems a bit more solid it might unfair to the guy, I think he would have the right to know into what kind of mess he is heading.
I also have to be a bit cautious because I am an entrepreneur and it would harm my business if my collagues and partner companies would know.

I have also noticed a curious thing. So far I have told every boyfriend candidates of being bipolar, all together 4 in 2 yrs. Three of them responded the same way: denial. They said they are sure I am exaggerating and if I tried I could control it completely. Have you run into this kind of reaction?
Aaaaarggh, so annoying. I really wish I did not feel morally obligated.
I guess I wish you would relieve me somehow from this by telling it is ok to hide it for awhile.