Well you have to ask yourself one question. Does the inability to store random files on the iPhone and iPod Touch affect the devices main purpose in a negative way?
Complaining about the inability to used device as a disk is as futile as complaining about Apples lack of SLI/Crossfire support. It just isn't going to get anyone anywhere.
Sorry, but if you can't tell there's a huge difference between my beef and your example, then you obviously haven't understood anything about this.
This is a feature that practically any other flash-device out there have. A feature any other iPod has. It's a feature many people use. It's a feature they have put effort into
removing. It's not like asking them to support DRM'd WMA.
I tell you where the complaining is going to get me: It's going to inform people that it is impossible to use this thing to put a document onto. That it's impossible to use for portable apps, that it's impossible to use as any other iPod have been capable of.
The complaining is making this feature-removal more well known, as I am certain I am not the only one having used this basic feature for years and years. Do a search on google on "disk mode" and "ipod Touch" (or "itouch") if you don't believe it's a feature that is commonly used.
Further, if you think I should just eat what ever they serve, because it is "futile", it's no wonder they put out such a product*–*You seem to be one of the people who doesn't matter if they cripple the thing. As long as you get to hand them your money.
To me, there's a clear line how much the OS can outweigh the crippling.
Edit: I asked myself the question you pose. The thing is, are we talking about the designed purpose (including the crippling)?
If so, no.
But in real life, as in "does removing disk mode from a flash storage device affect the main purpose and usability in a major way?" I'd give you a resounding YES!