If you are curious about federal child porn sentencing...

here is a link to the 400+ page report that the US Sentencing Commission published on the topic in December 2012.  The report's executive summary is only about a couple dozen pages, can be accessed at this link, and here are some interesting excerpts:

[S]entencing data indicate that a growing number of courts believe that the current sentencing scheme in non-production offenses is overly severe for some offenders.  As the Supreme Court has observed, the Commission’s obligation to collect and examine sentencing data directly relates to its statutory duty to consider whether the guidelines are in need of revision in light of feedback from judges as reflected in their sentencing decisions.

[A]s a result of recent changes in the computer and Internet technologies that typical non-production offenders use, the existing sentencing scheme in non-production cases no longer adequately distinguishes among offenders based on their degrees of culpability.  Non-production child pornography offenses have become almost exclusively Internet-enabled crimes; the typical offender today uses modern Internet-based technologies such as peer-to-peer (“P2P”) file-sharing programs that were just emerging only a decade ago and that now facilitate large collections of child pornography.  The typical offender’s collection not only has grown in volume but also contains a wide variety of graphic sexual images (including images of very young victims), which are now readily available on the Internet.  As a result, four of the of six sentencing enhancements in §2G2.2 — those relating to computer usage and the type and volume of images possessed by offenders, which together account for 13 offense levels — now apply to most offenders and, thus, fail to differentiate among offenders in terms of their culpability.  These enhancements originally were promulgated in an earlier technological era, when such factors better served to distinguish among offenders.15 Indeed, most of the enhancements in §2G2.2, in their current or antecedent versions, were promulgated when the typical offender obtained child pornography in printed form in the mail....

[M]ost stakeholders in the federal criminal justice system consider the nonproduction child pornography sentencing scheme to be seriously outmoded.  Those stakeholders, including sentencing courts, increasingly feel that they “are left without a meaningful baseline from which they can apply sentencing principles” in non-production cases....

The Commission concludes that the non-production child pornography sentencing scheme should be revised to account for recent technological changes in offense conduct and emerging social science research about offenders’ behaviors and histories, and also to better promote the purposes of punishment by accounting for the variations in offenders’ culpability and sexual dangerousness.

In addition, you might find intriguing and informative the lengthy discussion of child porn sentencing in the split Third Circuit panel decision in United States v. David Grober (where the majority, inter alia, faults the district court for allowing me to testify at the sentencing hearing).