aaaaactually, apparently people bruise easily when they get too much vitamin E (or on the flip side, way too little fat).

What I've heard about B12 (I have no article handy), is that the bacteria that make it are in our intestines, but they are too far down for the body to absorb B12. I've also heard that B12 will get destroyed somehow in the upper digestive system, so ingesting it doesn't help much. That's why there are sublingual tablets/sprays of B12, because you can absorb the stuff directly under your tongue (weird or what?). I use a spray, in the form of methylcobalamin (the package claims this is the only absorbable form. i don't think there's a consensus on any of this).

As far as general vitamins, supposedly taking those big vitamin tabs with 10000000% of everything won't get absorbed very easily, because your body isn't built to get so much minerals/vitamins that fast, and it will pass through without getting completely absorbed by the intestines. That's why you're supposed to take them with food, because the food (and the tab) will move slowly through your system and give more opportunity for absorption (who knows? I think it's all supposition).