Hi Dave
Well with a first degree that involved Social Anthropology and Sociology and an MSc in Computing Science your post certainly raised some interesting questions. At many conferences and discussions I have raised the issue 'why give students another device?' - do they really want it? The answers I have had cross between cultural, financial and technical issues.
- Cultural (and this true for most innovations) small devices are still viewed with suspicion by many educators. Mobile phones for example are seen as disruptive. This view changes over time, its interesting to hear the attitudes towards computers in the classroom by teachers in the 1980s compared to now. So for various reasons, an important one being increased familiarity with the technology themselves we know that the cultural issue can be addressed. We also need to recognise that we don't approach our small computing devices in the same way as their larger desktop or laptop relations. Mobile's become personal very quickly and that needs to be considered when managing the devices, I would suggest (and research needs to back this up) that the sense of personal ownership is probably higher for say a mobile phone or Ipod than for a desktop PC, which may often be shared anyway.
- Financial, small devices are seen as relatively expensive. This is a bit of an urban legend. Its true for any new technology that the price bracket is very high to begin with and when I worked directly in the mobile phone industry back the late 90s (I hate to say last century

the cost of devices was still very high and significantly value added functionality and reliability very low. The same was true with PDAs but that has changed a powerful web enabled contract free phone can now be found for below £30 and that is a lot of power for little money.
- Technical, there is a strong desire by the 'pro mobile educators' (many on this forum) that I have spoken to to see the technology as part of the woodwork and as someone who is often involved in usability it is a desire I share. However, the reality is we are still a long way off of that. I have been researching a 'device agnostic' approach to mobile learning mainly from the technical view i.e. letting the user use their own device, it is probably a bit of a Holy Grail for me, and there are lots of issues that need addressing, especially if you want to see interactive learning on these devices. However, unless we challenge those boundaries then we will change nothing.
I think this might contribute to an understanding of why we see the current approach to small device learning. Most projects centre around one device usually a PDA, which is brought by the institution with possible contributions from the user or parents. The PDA addresses the cultural issue because it is not a phone so not seen as much of a disruption by educators, it can also be controlled, it needs to connect to the institutions network to access materials not the mobile carrier. Also the financial issue is address because the PDAs can be brought en masse at a good price and again they do not carry the risk of mobile carrier charges. The technical issue is also addressed because you only need to be concerned about materials being available on one device. This makes development cheaper and testing much easier.
However, the use of PDAs in this way does not address an important cultural issue which you raise Dave - what does the learner want? They already have access to mobile phones, Ipods and playstatons portables but (at least in my observation) it is very rare to see a leaner elect to own a PDA, even smartphone ownership is rare. Some colleagues observe that perhaps this is because they are seen as business tools and still priced as such to the individual. Also, if we were to observe users we might find that each has a device of preference even if they own several different ones. That is another factor to take into account.
Some of the comments made in your observations about the disposability of devices may reflect an inverted snobbery e.g. 'It doesn't matter if I loose it, coz I got the cash to get another better one'. This attitude is actually encouraged by the mobile phone industry which relies on frequent upgrades to keep going. Although there are signs this model is changing.
So where does this leave us? The current device centric research and projects carried out by so many members of this forum is crucial. It provides important feedback about how to manage the devices and expectations of the learners in terms of using them. I also think (otherwise I would stop doing it) that my own and others considerations about device agnostic approaches are making useful contributions, especially in terms of pushing the limits of the technology. However for mobile learning to really be tested as a useful approach it needs to go mainstream, not just in schools but colleges, work based learning and universities as well. This will allow large scale, longitudinal studies to be carried out that will provide the macro sociology needed for future decisions.
In closing (my what a long post!) I would say that I doubt that mobile learning will ever be for everyone, some learners just will not want it: they are too settled in their existing methods, their device is too personal, their physical abilities do not suit it there are lots of reasons. That is why mobile learning should not be isolated in the curriculum but be addition to the options available to educators and learners. Perhaps the really challenge is to provide mass education with individual flexibility in approaches to learning - now there is a Holy Grail!