Vegans who start the diet as B12 sufficient adults can go up to 20 y before showing B12 deficiency symptoms due to enteric recycling of endogenous B12. In the meantime you can develop subclinical B12 insufficiency and do damage to your nervous system without knowing what is happening. Years ago I tried vegan eating without taking B12 and it didn't serve me well at all, I believe it was one of the reasons I didn't sustain it then, so since I resumed vegan eating almost 4 years ago, I've never wanted to take that risk and have taken fortified foods and supplements the whole time.
In our opinion, vitamin B12 in supplements is "full natty" since it is all derived from microbial fermentation, which is the ONLY natural source of B12 in the world (animals don't produce B12, they all get it from microbes). All B12 in supplements and fortified foods is from cultivated microbes. If cultivating microbes for B12 is "unnatural" then all of our cultivated food is "unnatural" and except for those few remaining hunter-gatherers who eat only wild foods, none of us is fully natural regardless of whether we use B12 supplements or not. I have a blog post about this: http://donmatesz.blogspot.com/2011/12/vitamin-b12-and-human-nutritional.html
We use fortified soy milk and nutritional yeast throughout the week, and on weekends take a liquid B12 supplement we get from Sprouts Markets (house brand).