The government passes laws to "enhance" certain foods with certain vitamins when as a nation people tend to be deficient in that vitamin. For example; if there is a lot of cases of rickets in infants, vitamin D would be added to baby formulas globally, etc. The reasoning is that less money is spent on treating the disease later and people are generally too dumb to care for themselves (which I actually, in this case agree with).
And as has been mentioned, YES, there is a recommended daily amount and there is also a "toxicity" level, which you shouldn't exceed. As also mentioned, your body is better at getting rid of access in some cases but not others so it kind of varies but I would generally try not to take TOO much as there is such a thing.