I recently turned a positive change for the team into a problem between me and one team member by communicating badly. One of the mistakes I made involved using e-mail when I should have talked face-to-face.
Lesson re-learned: The medium can change the message.
The hard part about getting a message across is that it passes through so many filters: The one between your thoughts and your words, and the ones created by different perspectives you and your team have. And there's the filter of the medium. The mistake I made was using the wrong medium for the content and the situation.
E-mail is great for passing along facts and data, coordinating schedules, and light relationship building (thank yous, well wishes). It's lousy for transmitting emotion or for dialog. And it not only stays around forever, it propagates as people forward.
The phone is a good tool for conversations, when some back and forth is needed to coordinate or to decide, but it works best when both parties are basically on the same page.
Face-to-face is the only good way to communicate when there are differences to be resolved, or there is strong emotional content. In those cases there are too many ways to be misunderstood, and you need to be where you can watch people's reactions and read their body language. And face-to-face is always the most effective relationship-builder.
The wrong medium can actually create barriers to communication. In my case, there was some emotional content to the information; e-mail tends to magnify passion. Also, my relationship with this person required some dialog, and e-mail just doesn't work for that.
Bottom line: the medium is inseparable from the message, so choose your means as thoughtfully as your words. When in doubt, the safest is to talk face-to-face.