Morra & Romano (2008) report on findings regarding student attitudes towards peer feedback on ESL & EAP writing and discuss the implications of these and similar results on the pedagogy of peer feedback. A few lines I thought were poignant, the first of which is regarding training to give feedback:
An interesting tendency observed in many studies of peer feedback in ESL and EFL settings is that students’ attitudes toward their peers’ reviews and comments seem to be conditioned by the amount and quality of training and preparation they receive in class previous to their actual participation in peer-response groups; that is, the more planned instruction the students receive, the better they seem to respond to the activity (Berg, 1999; Ferris & Hedgcock, 1998; Hansen & Liu, 2005; Hu, 2005; Mittan, 1989; Rollinson, 2005; Stanley, 1992). [20-21]
Giving students appropriate training and guidance on how to go about reviewing their classmates’ texts stands out as a crucial point when trying to generate a positive attitude toward peer feedback. 
And this regarding fear of giving/receiving feedback from peers:
Students also revealed that they avoided making critical comments in order to prevent conflict with their classmates. Some of them feared their writing being mocked publicly in the classroom. Teachers reported that, at the end of a peer-feedback session, most
students put away their compositions in their folders and never revised them. 
Together with appropriate and gradual training, the organization of small groups appears to be an effective technique to put peer feedback into practice since it might help to lower apprehension and fear and eventually lead to establishing a relaxed and stress-free atmosphere. 
And lastly this on combining feedbacks:
…there appears to be much to be gained from combining oral and written feedback in peer-response groups and from complementing peer feedback with final teacher feedback. 
Source: Morra and Romano (2008). University Students’ Reactions to Guided Peer Feedback of EAP Compositions. Journal of College Literacy and Learning 35:19-30.
To follow along with our Twitter discussion, please read through the transcript: http://chirpstory.com/li/90144
Maybe you have thoughts and experiences with feedback on writing?