(1) the reasons for doing it were framed well (emphasizing professional behavior) 

(2) clear examples of constructive, behavior-based feedback are provided to model how professionals write useful feedback

Criterion (1) is best accomplished during a live TBL with face-to-face communication.

Criterion (2) can be accomplished with online resources or, better yet, with a short on-line module that is coupled with completing the feedback assignment.

Yes, there are disadvantages to having the students walk away with hard copies of their teammates' feedbacks, to wit:

a) anonymity is lost, therefore most students (except mature ones) will be less willing to provide constructive criticism

b) under the pressure of "getting it done before you leave the room", some students will be less thoughtful in their comments, especially if they have to write (2 comments x 5 teammates = 10 comments) in a short time

c) as the course director, you will not have the benefit of reviewing the comments, and you will not be able to assess the quality of the written feedback.  With our medical students, our faculty grade the quality of each written feedback on a scale of 1-4.  While our grading is admittedly quite subjective, faculty feedback does provide each student with a set of impressions from someone with more professional experience.  

Attached are the grading criteria we use to evaluate quality of each student's comments; these are known by all students in advance.  Also, we have started to use blinded assessment of the feedbacks by two faculty, comparing the impressions of two persons, with a goal of decreasing the subjectivity factor.

Paul Koles, Boonshoft SOM