Answer:
Not Personal- instead of sending someone a birthday card we send them an e-card; instead of a call, we send an email, its the 21st century way of living where relationships are only with people we really want them with and not have to get personal.
Waste time from Work- Fact is that the average business worker today spends around 2 hours a day on email, creating less time from what needs to be done.
Security (Spam/Viruses/Spoofing)
Attachment size limitations
Push technology