^ You don't need a huge amount of Biotin, and in fact a percentage of your required dosage is actually manufactured in your digestive system, so the amount required varies from person to person. From what I've found, an actual RDI has not been established, possibly due to insufficient data.
From reading about it now, studies apparently show that the estimated average daily intake for people living in the US to be from 40 to 60 mcg/day in adults. Adequate Intake is placed around 30mcg/day, so you are quite possibly getting enough without even knowing it, and from reading about the symptoms of Biotin Deficiency (
include hair loss and a scaly red rash around the eyes, nose, mouth, and genital area. Neurologic symptoms in adults have included depression, lethargy, hallucination, and numbness and tingling of the extremities), you'd know about it if you were deficient.
Having said that, excess intake is not likely to hurt you (except perhaps your wallet). A statistic from the bottom of the linked page says that in infants with suspected deficiency, they are given 50-200 times the Estimated Safe and Adequate Daily Dietary Intake.
I would think that for a number of the elements you need, (especially the ones in small quantities in your multivitamins,) can be found spread widely among normal foods. Bear in mind that the multivitamin has it's quantities set specifically to counter the average (or expected) deficiencies of the population. Unless you have good reason to be worried about being deficient in a specific element, I wouldn't go overboard on supplements.