Very interesting article by The Washington Post's Editorial Board titled:
"Mr. Romney says that he can achieve this seemingly magical result by “broadening the base” for income tax collection. This, too, sounds great. In principle, everyone favors “broadening the base,” also known as closing loopholes. But everyone favors closing someone else’s loopholes: those of oil companies, say, or of plutocrats who park their money in the Cayman Islands. "
"Unfortunately, such inviting targets, to the extent they exist, don’t cost the government much in the overall scheme of things. The “loopholes” that cost most are deductions and other tax provisions that most Americans consider sensible, if not God-given, rights: tax breaks for employer-provided health insurance, which according to the Congressional Budget Office will cost $2 trillion over the next 10 years; for pension and retirement savings ($1.8 trillion); for mortgage interest ($1.6 trillion) and charitable giving ($600 billion). Mr. Romney hasn’t said which of these he would trim or by how much."