This is an excellent concept. I'm not so bothered about separating sites by category but containerising individual known bad organisations so that they cannot access anyone else's cookies is fantastic. However, I've only awarded 4-stars due to 1. low number and range of container colours available, 2. No ability to pre-assign sites by direct url entry - for some reason you have to open them first and then assign them then assign them from the drop down, 3. No ability to assign sites by domain - you have to open each site then assign them individually which is both laborious and prone to error.