58 Personal Content Experience: Managing Digital Life in the Mobile Age game, or capturing still images off a video recording, are typical exam- ples of the fourth category. There is yet another, perhaps even more infl uential, although less explicit, aspect: 5. More powerful methods of sharing have emerged. Sharing means sending, forwarding, or publishing on a blog, or making it available on a peer-to-peer network. Essentially it can also be understood as copying. Nevertheless, sharing, together with its strong associations to social behaviour, is one of the key activities in researching personal content, and also typical of many personal content types. In addition to the features described above, there are three obvious fundamental enablers that have made the content explosion possible in the fi rst place. These include, in no specifi c order: • the continuous increase in mass memory capacities; • the rapid commoditization of consumer broadband network access; and • active development of more effi cient content encoding and decod- ing algorithms (codecs). What, then, distinguishes mobile personal content from personal content? In section 2.3, we claimed that a key difference is in content quality, which is often related to the technical limitations inherent in mobile use. What other differences there are? In this section, we will consider the characteristics of personal content in general, and mobile personal content is then discussed in section 3.4. 3.3.1 Content Explosion The above discussion about content explosion leads us to the fi rst characteristics typical of personal content – its growth rate. It will heavily infl uence both system design of personal content management system and experience; for instance, Apple’s iPhoto 6 is prepared to 7 manage 250 000 photos. To put this in perspective, the mean number of captured digital images per month in the US was 75 in year 2005 (IDC 2005). With such a rate, it would take nearly 300 years for iPhoto’s limits to be met . . . 7 http://www.apple.com/ilife/iphoto/