1. They get credit for all the taxes they paid in other countries. They are essentially supposed to pay the difference between the US rate and the various foreign rates.

2. If you read some of the links, you'll discover that they are minimizing the taxes they pay on US revenue -- sales made right here at your corner Apple store -- by use of clever licensing agreements with their own foreign subsidiaries. Look at the interactive graphic on the Bloomberg story about Google, for example http://www.bloomberg.com/news/2010-10-21/google-2-4-rate-sho...