Be discreet with constructive criticism. A developer is much more likely to be accept casual suggestions and quiet leading questions than they are if the same is emailed to the entire group. Widening the audience is more likely to yield defensiveness and retribution. The team is always considering what your motives are, and you will be called on it and exiled if you degrade the work of others for self-promotion.
Actually, Jeff was quoting that from Dennis Forbes: http://www.yafla.com/dennisforbes/Effectively-Integrating-Into-Software-Development-Teams/Effectively-Integrating-Into-Software-Development-Teams.html