I use Picasa and haven't seen this problem, but let me know if this helps:
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How do I turn off face recognition and get rid of the Unnamed people file?
Turn off face detection by going to Tools => Options => Name tags and un-check the two check boxes. More info here.
Right-click on each individual person folder and select "Delete People Album".
To delete the Unnamed album at the top of the People collection, click Expand Groups (upper right corner), then select and delete all the faces.
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It's from
this website.