In "3G will bring sea change in biz models; users a key sales channel"* there are some interesting predictions for the future:

“Our research into the distribution channels for mobile content has indicated that the peer-to-peer model will gain traction over the next five years, with users essentially becoming resellers of content to others in their social environment,” explains Daniel Winterbottom, research analyst at Informa Telecoms and Media, publisher of Mobile Media, and author of the strategic report on mobile content business models. “But interoperability issues caused by the rollout of incompatible DRM systems will basically shackle what has the potential to be a very significant revenue stream.

Torsten Brodt mailed me that the Insights into Mobile SPAM, the world's first collaborative empirical study is out now:

The number of mobile messages and respective services shows tremendous growth rates with high profit margins. No wonder, the industry increasingly invests in rich media messaging and derivative business models. However, the growing concerns about unsolicited messaging - so called mobile spam - put these opportunities at risk.
[...]
Conducted in November - December 2004, the study analyzes perceptions based on 1'659 completed consumer surveys and 154 surveys from professionals.

Find here the Table of Contents as PDF (L.C.).