No telephone tag. Recently the National Archives Inspector General decided that he should coordinate with OMB before implementing a particularly innovative approach in his agency. Using e-mail, the IG in question had his idea completely staffed and approved by senior OMB management in 12 hours. As we all know, in the federal government, paper does not flow at that speed. I know my message won't interrupt the recipient at an inconvenient time, as a phone call might.
People read their e-mail only when they want.
In e-mail being brusk and to the point is not considered rude. When calling someone on the phone, most people feel at least some slight sense of social obligation to socialize for at least a while before getting down to business, and a little more after conducting business. No idle chit chat is necessary. People won't think you are rude, just efficient. E-mail makes it easier to keep track of what was said in important communications.