This is very true. In my wild animals in captivity class last semester we discussed it. Of course the % of these hybrids to each natural species isn't that large, but it happens completely on its own. Hence grolar bears (polar bear x grizzly) and the fact that much of the giraffe population is hybridized.
Seriously though, do these ball/burmese pythons get the same size as a burmese? Or are they like smaller?