The Christian Science Monitor hasa profile of various tax protestors who are refusing to file their taxes. Most of the ones profiled refuse to file their taxes due to their non-support of the US Military. Some don't file at all, some withhold what they believe is the military's share of the national budget. All of the protestors in this article claim that they donate what they would pay in tax to charity. It makes them all seem like righteous freedom fighters.
Of course, the US Government doesn't see it that way. The article points out, over and over again, that the IRS rarely goes after tax protestors. The problem with this theory is that the IRS does tend to go after very public protestors. I would imagine everyone in this article (which used real names and locations) will be getting a visit from the taxman. They may want to look up the names "Al Thompson" and "Irwin Schiff" to see what happens when tax protestors publicize their ways.
Remember, you must pay taxes. If you don't the IRS will catch up to you. All of the matching technology they have now means it will likely be sooner rather than later. So, be a good citizen and pay your taxes.