Don't forget, there is a limit on how far USB can go. According to USB.org: "USB specification limits the length of a cable between full speed devices to 5 meters (a little under 16 feet 5 inches). For a low speed device the limit is 3 meters (9 feet 10 inches)."
additionally, I did not know this and am glad I found out(even though I'll probably never encounter a problem like this) " Q6: You mean I can't make a direct cable connection like a null modem? A6: Correct. In fact, if you try this with an illegal A to A USB cable, you'll short the two PCs' power supplies together, possibly destroying one or both machines or causing a fire hazard."