I had to call three people to schedule things among us. Normally, I send out an email, or a bunch of emails. Does it take the same amount of time as a phone call? No. Why? Because in an email, you send out the message, and they get it and respond whenever they check their email. With a phone, either you reach them in that moment, or you have to leave a message, call them back, etc. All told, it can be twice or three times the amount of time you could have spent just shooting them an email. I used to call my friends from our home phones all the time to see if they could play. I remember always calling when my friend was in the shower, or eating dinner, or something else; I typically have bad timing with those things. But I usually didn't get the answering machine; one of her numerous little siblings would answer the phone--and proceed to tell me too much information as to why she could not come to the phone.
It is utterly disheartening to get answering machine after answering machine. I feel bad for telemarketers in that way; but I feel even worse for them, because I, like most other people, do not welcome their calls, and therefore do not pick up, or if I do pick up, I do not want to buy what they're selling, and therefore their call is fruitless, even if I'm polite about it.
Bottom line: email is the new contacting device. Not only is it more time efficient, it is also more organized. You don't have to go through "missed calls," "made calls," "text messages," and "voicemail" to get all of your messages and who called who. You have an inbox and an outbox, and it's easy.
What are the downfalls of email? It's not as personal. You don't hear his or her voice. The very fact that it is faster means that it is not as valuable. In other words, it doesn't mean as much as if you took the pains to call and call again.
In this changing technological world, the protocols of polite communication change inherently. I think people will understand if it's a business email, as opposed to a wedding gift thank you note. I could go on, but I think my message is clear. I much prefer emails, when they are the polite thing to do.