It can mean a lot of effort, yes, but in a lot of cases you can drastically reduce the number of items to re-tag by defining some simple relations between tags.

It can mean a lot of effort, yes, but in a lot of cases you can drastically reduce the number of items to re-tag by defining some simple relations between tags. For example tag A may require tag B to exist but not C, etc. In the end maintaining order always requires effort, if you have a hierarchical folder structure and you decide to add another category you have the same problem. And realistically folders are "good enough" for most situations, you can choose for each file how fine-grained the categorization should be and the mental overhead for finding a file is often not that bad.