Delete facetag

[gramsoft]

Using: exiftool -regionlist+="{Area={H=0.2,Unit=normalize,W=0.2,X=0.5,Y=0.5},Name=Joe,Type=Face}" pic.jpg - I have succeeded in making facetags in my application. They are visible in DigiKam, bur not in  Picasa. But how can I delete this facetag using command line?  

[StarGeek]

You could use something like
exiftool -XMP-mwg-rs:all= /path/to/files/

or
exiftool -RegionInfo= /path/to/files/