Crash reports consist of a text file with description of what caused foobar2000 to crash (a crash log) and a minidump file.
The minidump contains useful parts of memory collected to help identify why the application unexpectedly stopped working. It's relatively small and can be easily sent over the internet, but provides great help for the developers to pinpoint the cause of the failure.
No, such data is not important or useful. The reports contain only anonymous system parameters like CPU model and Windows version, list of installed 3rd party components and other necessary information to describe the state of foobar2000 at the time of crash. The crash reports can't technically include any data from other running applications or unrelated files on your computer. All content included with the crash report is deemed confidential and will be used solely for the purposes of analyzing the application failure.
If your crash was a result of a foobar2000 core bug, any information provided will be used to correct the bug.
If your crash was a result of a third party component bug, provided information will be primarily used for statistical purposes; in some cases the information may be forwarded to the developer of the problematic component.