I think we could be looking at a more integrated offering when we consider what else can be used on a phone.
Using mobile technology like
Musikube's it is possible to both recognise a song from a 3 second or so 'snapshot' or recognise it from a bar code printed on an ad, concert ticket etc.
Now if this is then integrated into the ITMS then someone with a mobile could hear music (for example in a bar), get the name, buy the track from ITMS onto their phone and then store it back into their Mac / PC next time they synched, all within a matter of seconds. Maybe there is a revenue sharing arrangement between Motorola and Apple for songs purchased this way.
Secondly, my understanding (please correct if I'm wrong) is that sales of ringtones is currently higher than sales on singles. This would enable Apple & Motorola to get into that market.
On it's own the technology seems limited (unless phones start getting compact drives like the iPod Mini) as most people buy phones to make calls, send messages. High end phone users (where the phones have more memory) are probably also more likely to want a iPod as they are early technology adopters. Start thinking about new ways of behaving from integrated technology and then a whole new market becomes available which pushes sales to both ITMS and potentially Motorola.
Of course, just adding ability to play tunes bought on ITMS increases it's penetration. People buying tracks using a mobile device will want to use it immediately so giving a phone the capability to play these tracks enables ITMS to be used from a phone, giving the opportunity to get much better market penetration (incidently it is unlikely a store which gives listening access for a subscription will work in the mobile field where data is charged per unit rather than a fixed-per-month cost like broadband)
This all becomes possible because only iTunes (ignoring the Real thing) can handle tunes bought on ITMS and that leads the market - people will want to buy one copy which can be used on all devices, that the publishers are willing to sell electronically (because the rights management is good). It helps Apple establish the standard in purchased music which then benefits Motorola sales.
It could be a very smart alliance.
Andrew