Error guessing is a testing technique that makes use of a tester's skill, intuition and experience in testing similar applications to identify defects that may not be easy to capture by the more formal techniques. It is usually done after more formal techniques are completed.
The main drawback of error guessing is it depends on the experience of the tester, who is deploying it. On the other hand, if several testers contribute to the process then the outcome can be more effective.
The defect and failure list can be used as the basis of a set of tests and this systematic approach is known as fault attack.