Not only that. It also can turn our reality into a lie. If we simply erase the things we don't remember then we are selectively altering history. It could make us believe a total lie simply due to the fact a very important piece of information that put it into proper context no longer existed. We see this a lot in the news. Yet this could become the reality.
The more I think about this the more I believe that there are RARE cases where this could save someone's life and be positive. However, most of the uses for this tool I believe are overwhelmingly negative things. Kind of scary actually.
A society full of people who lose empathy due to simply erasing the things that would leave them memories to relate to the pain and sorrow of others. A society full of people who have no idea that their memory of an event in history has been completely altered by deleting important contextual memories. Scary stuff.