I'm not sure if this is a bug or a feature, but it appears that sha1sums of files with control characters in their names, are printed with a "\" at the front of the sum. Here are two examples:
\65f13e107d10014321f7bb92e4560d1087289024 ~/.local/share/gvfs-metadata/label-Acres\\x20USA\\x202011 or \ec16ddba7d74c5c766da7c0a8d5dff5e6eb93136 ~/Mail/Re: By the way ...\n I can't find this happening for files with normal names. Dev. Running: Ubuntu 12.04 sha1sum version 8.13
