There's also a mental barrier that comes up when you see something unusual. I don't think about my expenses in pico dollars and I don't think about my important data in bytes. The worst part for me is that at $0.30/GB for storage and bandwidth the cost seems so low that I really don't even care if I'm using a full GB or just 12 bytes. Charge me the $0.30 and be done with it. If I can't glance at the service and guestimate how much it would cost me I'm not going to stick around long enough to find out.
Of course, the other thing to note here is that restaurants don't put dollar signs next to prices because they don't want people sitting there thinking about how much it costs.
The word "picodollar" is basically a dollar sign with a <blink> tag around it.
