>>I'm unaware of any snakes being extirpiated by the pet trade.

I don't think it's common in the U.S., but it does happen in some other areas, and perhaps here as well, in certain localities.

This is a quote from pg. 111 of Halliday's and Adler's Encyclopedia of Reptiles:

"Among specialist reptile-keepers, there is often a particular demand for species that are rare in the wild or have a restricted distribution, or those that are either attractively patterned or venomous.

Some species, including vipers in Turkey and Southwest Asia, combine all these properties, and many have been severely overcollected."