Nationalized Medicine

It is quite simple.  If the gov't is involved in something, it will want it to impose its will on that.  That is why if you are a govt supplier you must comply with govt rules, like no discrimination, and all that sort of thing.  OK, that's fair.  

Now think about this.  If the gov't funds health care, what new rules will it impose on users?  How much will it regulate how you live, what you eat, etc.?  Imagine a proscription against fried food (California is trying to ban transfats across the state now), a requirement for gov't approved exercise, a mandate to be a certain weight.  It is not far fetched.  It is predictable.  And it is just one argument against gov't involvement in health care.  

In out current model, insurance rates encourage and discourage behavior related to health.  That is why any good large company is so aggressive about promoting fitness in employees- to reduce the group rate, and it works very well.