Words can only convey so much information, and without nonverbal cues, body language, and gestures, we may not be able to interpret many of what is said to us properly. Mere facial expressions can say a lot in themselves, words aren't even needed in some situations, so when we are robbed of the ability to communicate through nonverbal expressions, the perfect example being e-mails and texting, many things can get misinterpreted and this can lead to difficult situations, whether they be with friends or with your boss at work.
We use body language and facial expressions to convey emotion whereas words are used to convey details; nonverbal expressions are like the music and words are the lyrics, without the music the song is not complete. As humans, we can easily pick up on underlying meanings just by looking at a person's stance or facial expressions (we may cross our arms to take a defensive stance, or we may widen our eyes to convey surprise).
There has been many times where I have been confused as to what someone else is trying to say in e-mails or text messages, I may think that a person is angry in their message when they were really being sarcastic or making a joke. Sarcasm and jokes are especially difficult to pick up on in messages because they both require a certain tone of voice or some sort of facial expression to go along with them, which messages can't always convey effectively.
One example of how e-mail or texts can be deceptive is the fact that some people consider all capital letters to be a good way to emphasize a point whereas others think of it as yelling. One of my father's coworkers sent an e-mail once that had several statements in all capitals to emphasize a point, but some others thought that he was basically yelling at them; there were definitely tensions that arose from that situation. So, we always have to be careful when we communicate through messages because much communication is lost without nonverbal cues.