The nightly builds for Flex SDK 4 now contain a new tool called swcdepends which can be used to analyze the dependencies between SWC files. This tool can be found under the bin folder of the SDK and the latest nightly builds for Flex SDK 4 is available at http://opensource.adobe.com/wiki/display/flexsdk/Download+Flex+4
Types of Dependencies
There . . . → Read More: Finding SWC dependencies