Perhaps due to the genetic makeup of the fast-spreading H1N1 strain of influenza -- which includes genetic elements from bird flu, swine flu and human flu spanning three continents -- there is considerable speculation that the origins of this virus are man-made.
I am not a medical specialist in the area of infectious disease, but I have studied microbiology, genetics and a considerable amount of material on pandemics. What seems suspicious to me is the hybrid origin of the viral fragments found in H1N1 influenza. According to reports in the mainstream media (which has no reason to lie about this particular detail), this strain of influenza contains viral code fragments from: Human influenza, Bird Flu from North America, Swine flu from Europe, & Swine flu from Asia.
This is rather astonishing to realize, because for this to have been a natural combination of viral fragments, it means an infected bird from North America would have had to infect pigs in Europe, then be re-infected by those some pigs with an unlikely cross-species mutation that allowed the bird to carry it again, then that bird would have had to fly to Asia and infected pigs there, and those Asian pigs then mutated the virus once again (while preserving the European swine and bird flu elements) to become human transmittable, and then a human would have had to catch that virus from the Asian pigs -- in Mexico! -- and spread it to others. (This isn't the only explanation of how it could have happened, but it is one scenario that gives you an idea of the complexity of such a thing happening).