I disagree. I think most people on this board are deficient in riboflavin. And riboflavin has no upper limit, is extremely safe to take on it's own.
Thyroid dysfunction and the MTHFR polymorphism are two things that lead to riboflavin deficiency, and require supplementation.
Alcohol consumption quickly robs the body of B vitamins.
Riboflavin is destroyed by light. Milk in clear containers loses it's riboflavin content. Folks who avoid dairy and egg products can quickly become deficient in riboflavin.
Riboflavin is not stored in the body and must be gotten from the diet on a daily basis.
Taking a b-complex along with extra riboflavin is important because riboflavin works together with the other b-vitamins. I do agree it's important not to get too much B6, or B5, and many b-complex vitamins have too much of these, but that doesn't mean all b-complex vitamins are bad.
MegaFood has a good b-vitamin with reasonable dosages. And my favorite is the sublingual b-complex from Source Naturals.