Also, I would add mega-RDA vitamin B supplements to the "worst" list.
May I ask the obvious question... why?
Individual requirements for B vitamins vary widely in individuals, especially those with a northern European genetic heritage. Perhaps these genetic abnormalities arose in an evolutionary "attempt" to find alternate metabolic pathways to compensate for a lack of folic acid during a long, dark winter without greens. The mega B50 or B100 formulas (50 or 100 times the RDA) may help such individuals. For others, they are at best a waste of money, and at worst can be damaging. If I take more than 2 or three times the RDA of B1 and B2, I get manically depressed. LEF's life extension mix leaves me almost psychotic after a few weeks of use.
Megadose of Niacinamide inhibit SIRT1, niacin while useful to control blood lipids has undesireable effects on energy levels and perhaps on lifespan, and probably shouldn't be used by healthy individuals.
In short, it's a one-size solution that isn't suitable for most people, even those without the time to determine what works for them. In a sort of Gresham's law for supplements, the prevelance of Mega-B multi's makes it hard to find a good quality B supplement with a more moderate dosage. (Centrum won't do.)