I just discovered the reason why TimeMachine was backing up so much data. I forgot to exclude my Maven and Ivy repositories 
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Here is a good tip to discover which files are backed up. You need to have the Developer Tools installed.
When TimeMachine backs up
- Launch /Developer/Applications/Instruments
- Select File Activity
- Open the default target combo box and attach the backupd process.
- Start recording
- Enjoy the list.
I wish there were a less geeky solution.
Shorter, put this in a “seebackup” shell script:
#!/bin/sh
opensnoop -n backupd | sed -ne ‘/\/Backups\.backupdb\// s,.*\.inProgress/[^/]*/,/Volumes/,p’
Here’s a simpler method:
% sudo fs_usage backupd