Between 1996 and 2006 an estimated 99,000 Burmese pythons were imported into the US, of these an estimated 30,000 now live in the Everglades. Worse yet, they, along with released Boas, are now breeding.
Additionally, there are an unknown number of reticulate pythons, yellow anacondas, and green anacondas roaming around Florida. When you consider that a number of these species grow large enough to eat white-tailed deer and alligators, you can understand, I hope, why this is a problem. These snakes can also survive anywhere an alligator can survive, so unless something is done you can expect to see them showing up in places like Georgia and Louisiana within the next couple of years (one telemetered python traveled 48 miles over the span of a couple of months).
This kind of thing has the potential to have catastrophic effects on the environment, the already endangered Key Largo woodrat are favored prey items, and smaller pythons are competing with the endangered indigo snake for prey.
Large snakes do not make good pets, even experienced professionals do not like to handle them alone, and several people have been killed by their snakes. So do us all a favor and stop buying them, and if you have one do not release it into the wild.
Update 1: Science Daily also has info on the subject
USGS Maps Show Potential Non-Native Python Habitat Along Three U.S. Coasts
Burmese Python Consumes Bobcat
Update 2: Then, of course, there is this:
“We’re seeing everything from boa constrictors and pythons to iguanas and a few alligators.”
When they cross paths with a large reptile, firefighters “do the best we can to work around it and move on, and wait until it clears the area before we go in,” Dueitt said.
Here is a picture to illustrate the problem (Source: NPS Photo)