Compare-a-Face is an interesting app included in the FamilySearch.org Family History Activities.
This collection of activities is derived from the apps used in the Family Discovery Centers located in Salt Lake City, Seattle, Lehi, Layton, Ogden, and St. George. Only two of these, Salt Lake at the Family History Library and Seattle are directly linked from the FamilySearch.org website. There may be more of these Discovery Centers and you are welcome to leave a comment and let us all know about additional Family Discovery Centers.
The Compare-a-face is interesting but if you have few or no photos in the Memories section of the website, your choices for comparison will be limited.