Cuz it will suck away your battery life more than the HDD would. Even with NAND streaming over WiFi will be a battery hog. And that streaming stuff leaves the possiblity of thievery open. Also, WiFi everywhere (unlocked WiFi) isn't here just yet and may not be happening any time in the near future.
I do like your idea of flash memory though. It will suck for those with libraries in the 30 - 50+ GB range... but us smucks with about 14GB or less would love to see an iPod with flash memory and supurb battery life. iPhone sized of course with that kick arse interface. 32 - 64GB capacity.... Yeah... I like that.
Sure, in the beginning it would, but things improve through time: battery life, more efficient use of power in wifi devices etc. What I'm really talking about is my "ideal" device and what wifi can really do for all of us in the (possible) near future. I'd rather house everything in one location rather than duplicate files in mulitple areas.
I understand the idea of "thievery" by stealing from your own wifi stream, but to be honest there are secure ways of defeating most of these issues. In terms of wifi access, yes, you're definitely right. It is rather limited, but it is a rapidly growing thing, and in my area (Atlanta) we will soon have citywide wifi available to everyone so the idea of streaming all of media wherever I am is growing increasingly appealing to me.
Ultimately, I posted my "dream" wifi device idea because people kept of poo-pooing the idea of a wifi idea: "Why do I need it?" "What's so great about it?" Well, I want it, and I think once the potential is realized, *EVERYONE* will want it as well. Think of the *future* advantages of a wifi ipod:
1. Smaller, thinner, sleaker, more compact.
2. Give Apple (and others) more room to develop a better UI, experience, better features, etc. instead of additional worry about: how are we going to fit a harddrive/flash drive in here?
3. Media space is no longer an issue for a portable device, because all of our content is streamed.
4. Less moving parts, more durability, etc.
Imho, this is the future. As technology gets better, power consumption on wifi devices get more efficient, etc. people will understand why people like me WANT wifi in their iPod.
w00master