I want to try to push this concept, given the problems in having a reasonable discussion with the current "makers" and "takers" stuff, and based on my consciousness of coming to the close of my lifecycle.
Over the course of a lifetime, people are always dependent at some times and usually are productive at others. So the percentage of Americans who don't pay federal income taxes is higher than 47 percent, because that statement includes both the young and the old. There's exceptions: people on social security start paying income taxes when their income exceeds $25,000 (a fact I just had to look up), and people on civil service retirement (moi) pay income tax on the portion of their annuity representing the government's contribution. And, as has been discussed extensively on liberal blogs, employed people pay the payroll tax, drinkers and smokers pay the excise tax, drivers pay the gas tax, etc.
[Updated: Matt Yglesias.]