Can these tablets be cut in half?

I can't think of anything in this world that can't be cut in half

aren't all b12 supplements manufactured in the same way? big vats of starch and bacteria? Why should we pay extra for "vegan" b12?

I'm not sure what you mean by "extra", considering $25 for a 6 month's supply of B12, folic acid, and B6 seems very reasonable. As you may know, not all supplements are vegan or even vegetarian, as the tablets themselves may contain gelatin or other odd ingredients. These are labeled vegan because they are advertised for those on a vegan diet (though B12 supplements are recommended for others as well), and because none of the ingredients contain animal products.Not all B12 supplements are created equal, as is true for all supplements. I have not taken these personally, but I do take the DEVA multivitamin, which also contains B12. They are excellent vitamins, and I've been in great health since I started taking them (I think it's been at least 2 years since I was sick).

It is my understanding that B-12 comes naturally from animals and that non-animal B-12 is not effective, correct?

B-12 doesn't come naturally from animals. B-12 is made by bacteria living in the soil and pond water, and animals in the wild get when they consume some of the soil while grazing, or when they drink pond water. Farm animals (the source of almost all the meat sold in stores) are give B-12 supplements that are mixed into their feed or through injections. It is more efficient to get our B-12 directly instead of filtering it through the animals. That's why so many people, whether vegan or not, are deficient in B-12. You can read up more on nutritionfacts.org or the resources provided in the other answers.

Why do they have to use xylitol? Many studies have linked it to cancer.

And yet, at quite low doses xylitol can act as a fairly potent laxative. Not something you want to give a person -- especially a child -- with chronic digestive problems, which is one of the reasons a person might need to supplement B12. Just a paranoid warning, but not totally.