How many times should the same piece of money be taxed?

So if I get a job and earn some money it's taxed. Some of it is taxed and some goes into unemployment and SS. When I collect unemployment or ss it's taxed again. If I get a tax refund that refund is taxed again. And when I die, the death tax kicks in an it's taxed again. I think most people probably go through these steps an are probably taxed more often (investments, capitol gains etc.).