Depends on how you define conspiracy theories. Do I believe that there are conspiracies aplenty, sure. Cigarette companies come immediately to mind as an example. And I'm sure I could think of a couple of government ones if I tried. (Tuskagee, anybody?) I really don't think there will ever be a shortage of the privelaged and/or the fanatical who think that they know what's best for the rest of us, though.
My problems with many of the more grandoise ones, though, is that they require me to believe too much psuedoscience, or that you have too many blindly loyal people with stories that are too hard to back up. When you have to think in circles to come to your conclusion, maybe it's time to think things just happened the way they did.
And, of course, if the powers behind most of the grandiose conspiracies are as all knowing, all seeing, and all powerful as the conspiracy theorists claim, as powerful as they'd need to be, than what're all these people doing running around free pointing them out. I don't think we'll know what the real dirt is for a long, long while.