“Since I do not want my private conversations looked at by those out to embarrass, the only course of action is not to correspond in cyberspace,” Mr. Bush wrote from his old address, G94B@aol.com. “This saddens me. I have enjoyed conversing with each of you.”

But in the interceding eight years, as BlackBerrys have become ubiquitous  and often less intrusive than a telephone, the volume of e-mail has multiplied and the role of technology has matured. Mr. Obama used e-mail to stay in constant touch with friends from the lonely confines of the road, often sending messages like “Sox!” when the Chicago White Sox won a game. He also relied on e-mail to keep abreast of the rapid whirl of events on a given campaign day.

Mr. Obama’s memorandums and briefing books were seldom printed out and delivered to his house or hotel room, aides said. They were simply sent to his BlackBerry for his review. If a document was too long, he would read and respond from his laptop computer, often putting his editing changes in red type.

His messages to advisers and friends, they say, are generally crisp, properly spelled and free of symbols or emoticons. The time stamps provided a window into how much he was sleeping on a given night, with messages often being sent to staff members at 1 a.m. or as late as 3 a.m. if he was working on an important speech.

He received a scaled-down list of news clippings, with his advisers wanting to keep him from reading blogs and news updates all day long, yet aides said he still seemed to hear about nearly everything in real time. A network of friends  some from college, others from Chicago and various chapters in his life  promised to keep him plugged in.

Not having such a ready line to that network, staff members who spent countless hours with him say, is likely to be a challenge.

“Given how important it is for him to get unfiltered information from as many sources as possible, I can imagine he will miss that freedom,” said Linda Douglass, a senior adviser who traveled with the campaign.