File has different owner if examined using `sudo`
These files are owned by UID 99, which is the unknown user.  These files were, perhaps, initially created by an account that is no longer on the system, or a "different version of yourself" that was migrated from a previous version of the OS, etc.  To avoid confusion, when a normal user inspects these files, they appear to belong to whoever is viewing them.  When root inspects them (via sudo, for example), their actual owner is shown.

The following describes this in greater detail:

http://googlemac.blogspot.com/2007/03/user-99-unknown.html