The problem is that those mental maps and models leave the project when the tester leaves. These are all modeling questions, and there are tools and techniques that can make it easy to record our understanding of how the software works. Exploratory testing is useful and necessary, but not sufficient. Exploratory modeling urges that one of the outputs of the exploratory tester's efforts be to help construct a model of the software's behavior. Making this model enables the tester to do a more thorough job of exercising the software.
Some people view exploratory testing as happening alongside more formal testing.
Some see it as happening instead of more formal testing. Be the first person to add a comment in the Wiki Forum at page ExploratoryModeling .