It is one of the basic truisms of records management theory: that decisions regarding retention requirements are made based on their content and 'regardless of format'. This was an especially useful mantra a decade or so ago when some users would otherwise see the electronic version of a document as some alien construct, completely divorced from its paper counterpart.
Its still a mantra we cling to today and trot out as our first instinctive response, but its limitations are becoming more and more obvious, for example when it comes to email. Yes, its easy for us to say to our users that they must manage the contents of their inbox not as emails, but according to the content they contain but this is seldom reflected in reality. The simple fact is that the sheer volume of emails faced by users makes this virtually impossible to achieve and the majority of decisions taken regarding the fate of email are either taken on an individual ad hoc basis ("I don't think I need this any more") or en masse ("I've run out of space allocation so lets delete all last year's emails/all emails with large attachments etc").
The news that UK phone companies are now bound by law to retain information about all telephone calls and text messages for one year sounds a further death knell in the practicality of the 'regardless of format' concept. Even though this data might be used for one of three levels of enquiry the decision has been made that all such information must be retained for the same period: regardless of content, subject or any other criteria. If its information about a phone call it is kept for 1 year - and that is retention based purely on format and 'regardless of content'.