I'm currently debugging an Android app that has a data directory size that's increasing to several hundred megabytes, not good! It should be only a few kilobytes.
To find out what is going on I needed to see inside the data directory, but this is only possible if the phone is rooted, I don't want to that, so I needed an alternative.
After some browsing I found an github project that converts android backups into a tar (compressed file) format.
I've compiled the jar for you to download, but if you don't want that, you can compile it yourself. Once you've downloaded the jar just run:
adb backup -noapk com.instagram.android java -jar path/to/abe-all.jar unpack backup.ab backup.tar
Then extract the backup.tar file with your favourite compression utility, and you'll have a whole load of exciting files!