By default, CrashPlan backs up everything in your home folder including all hidden directories (directories starting with a dot (.). This would include some directories your probably don’t want backed up, such as ~/.local/share/Trash (your trash) and a bunch of other hidden directories.
Fortunately CrashPlan’s file exclusion feature includes a way to specify exclusions by regular expression. Simply go to Settings > Backup and next to Filename Exclusions click the configure button.
Check the box for Regular Expression and enter this:
Click the plus sign, then ok, then save again.
That will exclude all the dotted directories from your backups.
Have any filename exclusions that you use on your backups? Feel free to share your rationale in the comments below!