Typing patterns as an authentication method

Bruce Schneier's blog points to a user authentication technology that uses individual typing characteristics for identity verification. Similar to the way some detections systems claim to identify a person by their gait, PSYLock does psychometrical authentication based on the notion that typing behaviour of individuals has unique features that cannot be copied. The degree of security is dependent on the typing sample length used to authenticate users. Some of the comments on Schneier's blog point to some problems with the concept, such spoofing the system, which uses a sample phrase,  by trying to match the acoustical pattern/rhythm of the typing through practice.