I like to use scientific names for all the reasons above. It breaks down sometimes though. Morelia spilotes is the carpet python, but the whole morelia genus is somewhat fluid, and spilotes in particular. In this case it's probably more accurate to say carpet python, than try assign a genus species subspecies name.
I bet it's the same with some spiders. I have a euathlus 'pitchangui' blue femur. So while people agree on the genus no-one knows for sure whether the green femur is a different race, subspecies or species from the blue femur or maybe even just a colour variation.

It seems the closer you look the muddier the picture becomes. You can't even claim that just because the mate and produce viable offspring that they are the same species, because you get such monsters as the carpall or barpet.

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Snickers
Snakes - Carpet Pythons1.1 Bredl's Python (Neville/Luna)1.1 Jungle X Carpet Python (Molly/Arthur)0.1 Diamond X Carpet Python (Aurora)
Inverts - Tarantulas0.0.1 B. bohemi - Mexican Fireleg (George)0.0.1 B. emilia - Mexican Red Leg (Ginny)0.0.1 B. smithi - Mexican Red Knee (Fred)0.0.1 B. vagans - Mexican Red Rump (Charlie)0.0.1 C. fimbriata - Indian Chevron (Snape)0.0.1 C. cyaneopubescens - GBB (Mosag)0.0.1 E. sp. "blue femur"0.1.0 G. rosea - Chile Rose (Aragog)0.0.1 L. parahybana - Salmon Pink Birdeater (Hagrid)

The core reason there is such a muddle is the chism that exists in taxonomy at the moment - there is still debate as to what is and isnt a species.

Molecular data tends to split species into new ones, because you can have fairly large molecular differences (relatively) between morphologically identical species over geographic range. This is especially troublesome in hybrid zones, where two species co-exist in the same habitat and breeding occurs. It can also happen with "ring species", where a physical barrier seperates a species into two or more groups along a geographic area before re-joining them further past the barrier.

The easiest way to think of this is with a gorge - before the gorge starts it is flat uninteruppted land. Lets imagine the gorge opens W-->E and stops N-->S migrtaion and S-->N migration. Species A exists with no barrier to disperal before the gorge. As you move East say, the gorge opens and limits migration. You have two sub-populations of one species on either side of the N/S divide. Imagine this barrier is large - it covers many miles. You will get gradual inbredding on the N/S edges that accumulate different alleles (genes).

Eventually, you could have 2 molecularily different "species" that have branched from one. It gets even more complicated if specie's A natural range is wider than the barrier, because the two new species can then meet up with the original species and form another hybrid zone between 3 species...I guess this ties into what you were saying Snickers, because this happens a lot in the wild and can lead to confusion in the taxonomy of a particular group. There's a lot of arguement over splitting or clumping groups of species.

Anyway, the point i'm making is that its very difficult to classify a species using only molecular or morphological data, and thats where the arguement arises as people try to decide which is more accurate and reliable. It does often agree however, just now and agin there can be surprises.

In a lot of arachnid phylogenies (evolutionary trees), the original morphological data hasnt been re-assessed using molecular data to see if a more accurate picture can be made of seperate species and how they evolved. It will get there in time, but its difficult to sample every population of a species over its entire range and analyse any differences...especially as funding in spiders is not as high as say...more significant insect crop pests.

Lastly: I don't know enough about snake genetics to say 100%, but what you describe is probably still considered a species. If you have two snakes breeding together and they produce a carball or whatever, then it might still be the same species, but expressing one or several rare recessive alleles that change its morphology (how it looks/behaves). I might still be a carpet python or whatever (if it was bred by crossing same species parents) but under taxonomy...well, I guess its a 'variety', similar to plants. Its not justifiable to call it a new species because they are probably the same genetically barring a few allele frequency changes caused by continued inbreeding. It would be notated by adding var. after the species name and adding whatever it was - 'carball' or whatever.

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"All I know is my gut says maybe"

Brachypelma albopilosum (Charlotte)
100's of Harvestmen
Member of the BAS and AAS.

only hybrids that are fertile are considerd species, for example Psalmopeus irminia and Psalmopeus reduncus can breed together but the resultant offspring are infertile and cannot breed, as such if a 'carpondro' is fertile it is a new species and will have to be classified, but if not then it is not a species, but an abberation.

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1.1 CWD
0.1 BD
1 HUSKY x STAFF
1 FOX TERRIER
1.0.3 RABBITS
1.0 CHINCHILLAS
63 FISH
0.1 CHILDREN
1.0 Ringneck Parakeet

Ah yeah, I forgot to factor that in my snake musing - are those morphs fertile?

Something that has come to the fore recently in pest control that is relevent is that sometimes infertitle hybrids can maintain degrees of fertility -its difficult to explain, but in numerical terms,a cross could be say...90% infertile. There is still a chance that it could somehow pass on its genes. This also confuses the species concept, although its more common in plants than animals AFAIK

__________________
"All I know is my gut says maybe"

Brachypelma albopilosum (Charlotte)
100's of Harvestmen
Member of the BAS and AAS.