I completely agree with you, but the user might have been trained by his iPhone to relate the speed of the spinner to the data transfer speed. (The spinner in the status bar of the iPhone indicating network activity has a different speed when you're on EDGE or GPRS versus when you're on 3G).
You raise an interesting point. That throbber does have (exactly) two speeds — but if you are experiencing EDGE-speed transfer rates over 3G for some reason (low connectivity), it still spins at the normal (3G) speed. So it’s not quite the same as what’s being suggested here, as I understand it (a variable speed throbber tied to current transfer rates). Certainly an intriguing design decision though.
I have to imagine the slow speed of the EDGE throbber is saying, “Expect this to take awhile. Look, I take 6 seconds to even spin around once…”
Thus if we were to take the concept to the Web, it might make more sense to tie rate of revolution not to speed, but rather to expected time to complete (based on speed and file size) such that we expect the spinner to make exactly (say) 15 revolutions before the upload completes (with a min and max cap on revolution speed, of course).
I still maintain that if we know this much information, though, we ought to just show a progress bar and optionally text as well.
