There are two types of customs clearance, China Customs and US Customs.
U.S. Customs does not matter, anyway, you are a tourist, as long as you do not bring contraband, such as food, drugs, pirated disks and so on, it is fine. Daily necessities do not have to report, with a computer camera also do not need, but if you bring more than 10,000 U.S. dollars in cash traveler's checks money orders to report, but is a routine ask, it will be fine. Valuable jewelry watches do not wear, because more than the value of the customs declaration, more trouble, with some travel essentials on the good, the United States can buy anything. When you go out of the United States, the U.S. Customs will not check, just on the airplane security check to pass, the same as the domestic security check.
Returning home when the customs should be reported in theory, but the general customs is a random check, China in and out of too many people, checking is not so strict. But this year is special, August is the Olympic Games, will be more strict, so if you buy more things, such as computers and so on, or report more insurance. If you just buy a few clothes and shoes, rip off the tags and bring them back, you won't be able to check them.
Most digital products in the United States are not warranted in China. The camera is not available, because it is a precision instrument; the computer seems to be not available, I'm not sure, because my hp back to the country no one care to repair. And digital products do not feel much cheaper.