The authors use their own experiences with social software to argue for the need for caution in its uses in education. They particularly draw attention to difficulties in engagement, the effects on identity, an emphasis on superficial issues, lack of coherence, and problems with authenticity and trust. While Facebook and Second Life appear to have potential for educational applications, the disquiet associated with them may need to be taken into account: and this can affect both students and their teachers. One of the authors is a student on an online course and extracts from her blogs and journal capture the emotional and psychological effects of engaging in these new worlds at the time it happened. Both authors have noticed changes in their responses over time and point to the need for integration and coherence for "virtual identities" to play an appropriate part in higher education. The paper raises more questions than it answers and suggests that there is an urgent need to theorise online identity, the roles of academics and students, and the codes of practice in such environments. If social software has a serious place in academic life, these issues will need to be widely debated.