It is still best for everyone in the long run if you avoid inbreeding at all costs - especially in well-established morphs.
Inbreeding is unfortunately a very common practice, and there are arguments both for and against this practice.
Most people get into snakes in some way or another to see a return on an investment. *NOTICE: I NEVER say "ALL people"* Consider this scenario: In order to do see a return on their investment, many people will buy one animal with a trait (or that is just heterozygous for a trait), and something to breed it to. They then save back all of the offspring, and breed them back to the parent with the trait.
As it was brought up earlier in this thread, yes, this can be done to propogate a trait that is extremely rare, however it is commonly used to make a quick buck.
So what happens to the genetics involved here when the offspring bred back to the parent yield offspring that the breeder wants to sell? A lot of times those animals will be bought by someone who similarly wants to make a quick buck, and buys the animal in question and something to breed it to, saves back all of the offspring from that mating and mate them back to their orignal parent animal with the trait... and so on.
The argument that was brought up against inbreeding here, was the mention of genetic defects that could be harmful to the animals. Any good geneticist (or anyone who has had a good class on genetics) would see a problem with the scenario I've illustrated - which has gone on in the reptile trade for DECADES.
Some scary bad genes are carried by all species. You know how people make fun of each other with the "that's what happens when cousins marry" kind of thing? The point it that is you mate related individuals, any of the strange recessive genes that they share (because they are related) but don't express (because they are recessive, and rare) are much more likely to be expressed in their offspring (because both parents, being related, are more likely to carry the same weird scary recessive genes). That's why there are some seriously scary traits in humans that are usually not seen because it is usually unacceptable for relatives to mate or marry.
Basically, if you would have a problem accepting people of a certain degree of relation mating with each other and having kids, DON'T do it with your reptiles!! And if you wouldn't have a problem with human siblings breeding, or parents and children breeding, DON'T HAVE KIDS, and please still don't do that with your reptiles!!!
Just my thoughts on the matter here.
~Rebecca
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1.1 Ball Pythons (1.0 '05 Ghost, 0.1 '03 Normal)
0.1 Dumeril's Boa '04
0.2 American Pit Bull Terriers (40 lb darling lap dogs)