Like most of the other reviewers, I found "The Blot" disappointingly slow and preachy, with some flaws in its dramatic structure. However, the film does have value as a study of 1920's social conflicts that people nowadays may not realize even existed. For example, the heroine's mother looks down upon her wealthier next-door neighbors because their money comes from selling shoes (while at the same time she steals from their garbage can to feed the pet cat she can't otherwise afford). How many people today think there is anything "low" about selling shoes? When a group of teenagers boisterously starts an impromptu jazz-piano-and-dance session in a living room, the message is that these kids are vulgar and out of control. But many parents in 2007 would get down on their knees in gratitude if their teenagers engaged in such innocent pastimes. If it wasn't for filmmakers like Lois Weber, such changes in popular opinion would go by unnoticed. In addition, the film does succeed in portraying some of the small heartbreaks of "genteel poverty" and neighborhood rivalry with genuine feeling. And aren't voters everywhere still arguing about whether teachers are fairly compensated for their work?
Wikipedia claims that "The Blot" is unusual for the time in its use of natural light and real locations.
According to film historians, Lois Weber was considered one of the best and most important directors in her day. The fact that modern viewers have trouble relating to the way she tells her stories is in itself evidence that times have changed in ways we might not yet understand. Just one of the many arguments for film preservation.