I can understand the "that's not the bottleneck" argument. But the problem with going too far down that road is this: Imagine if you had to wait one second for your keyboard to respond to any key you type (and one second between keystrokes). You could still produce awesome code and be a great hacker, but can you look me in the proverbial eye and tell me that this would not handicap you in some way? Think about the commands you type really quickly on the command line without a second thought. Think of the messages you send off to friends really quickly.

Generalize this to the experience of using the Internet. Since great entrepreneurs are relentlessly resourceful, they can make great things come to pass using a 56k dialup connection, but I'm sure you wouldn't want a connection as slow as that. Why? If you want to think of it in terms of the argument you made above, then it's obvious that the bandwidth is unimportant because your connection is idle for the bulk of the time you spend using the Web.

The important thing is not thinking of this as a comparison between how much time you spend typing versus thinking. It's more about maximizing the responsiveness between you and your computer. The less friction there is during these small bursts of interaction, the better.