Bill Gates' bankroll is whatever portion of his moneys that he dedicates to poker. If he bought into the WSOP ME, his bankroll was never $3K. Basically, one's bankroll isn't JUST the money you have online, it may even be money you have in your bank account.

I only keep ~20 BIs online and keep the rest in my bank account where I feel it's safer and is earning interest. However, the 20 BIs online plus whatever is in my bank account (that is set aside for poker) is my poker bankroll...NOT just the 20 BIs online.

Players also seem to have a problem with having moneys on two or more different poker rooms. There really shouldn't be a distinction between "my Full Tilt Poker bankroll and my PokerStars bankroll" even though I see many players make this distinction.