Business card? He has your profile

Certainly not his e-mail account (10 gigabytes), his virtual Rolodex (1,684 connections on LinkedIn and counting), the number of corporate boards he sits on (seven), the number of companies he has invested in (more than 60), the number of computers he mans in a single sitting (three), the number of windows he has open on his desktop at any one time (a few hundred) or the way some of Silicon Valley's sharpest minds describe him (with mega-respect and affection -- one friend even refers to him as His Reidness).

Just as the power of technology is expanding at an exponential rate, so too is Hoffman's influence. Yet he's so intent on driving technological change that he is reluctant to slow down long enough to spend a few hours a week with the personal trainer his friends hired to downsize his beefy frame.

The only thing that isn't big is Hoffman's ego. He receives scant attention compared with the entrepreneurs he has bankrolled.

Until a few weeks ago, he and his wife, Michelle Yee, shared an 876-square-foot, two-bedroom apartment in Mountain View with 400 of his books and 900 of his DVDs (many hundreds more are in storage). He agreed to move to a larger house to make room for friends to watch movies or play an addictive German board game, Settlers of Catan. He married Yee, his college sweetheart, in the same understated way: before a justice of the peace and three witnesses.

Hoffman is just as down-to-earth at LinkedIn's rapidly expanding headquarters. He would prefer to occupy a cubicle if not for all the confidential, high-level meetings that pack his days. Instead he works in an unpretentious office that's chaotic and strewn with books, yet he can still find anything he's looking for in seconds.

He is adept at what he calls "context switching," effortlessly moving from meetings to e-mails to phone calls to ordering another book or DVD from Amazon.com. He starts and ends each business day with meetings over breakfast and dinner. Weekends quickly fill up, too. The only thing that is sacrosanct is date night on Saturdays with his wife.

Said former LinkedIn executive and early Facebook employee Matt Cohler: "He's oblivious to the external noise. He just homes in on the stuff that really matters."

Hoffman is like a life-size version of your favorite teddy bear, with his untamed hair, round, stubble-covered cheeks and easy smile. His uniform consists of faded polo shirts tucked into worn jeans and paired with running shoes. The only stylized touch: modish eyeglasses his wife picked out for him in eight minutes, the extent of his patience with shopping or anything else that takes him away from his fixation on LinkedIn.