This argument is getting old. From http://www.modelaircraft.org/files/FAAARCFAQs8.pdf

Though there is some variation between the language in the FAA Advisory Circular and the
AMA Safety Code, AMA believes its guidelines meet the intent of the Advisory Circular.
When published in 1981, AC 91-57 presented a very general policy statement regarding model
airplane operations and a philosophy that model aviation should operate safely and cooperatively
within its communities. The Advisory Circular is not regulatory and the conception of the AC
did not go through the rigor and public scrutiny required of a rulemaking process, and by nature
the AC allows for situational awareness and personal judgment.
In February of 2007, the FAA did publish a clarification of AC 91-57 in the Federal Register.
This posting was made to clarify the intent and application of AC 91-57. It states that the
Advisory Circular only applies to model aircraft flown for recreational purposes and not to
commercial/public use unmanned aircraft systems (UAS).
There is a difference between the language in the current FAA Advisory Circular and AMA's
implementation of this guideline in the AMA Safety code. AMA believes the only significant
risk posed to the manned aviation community by aeromodeling is when model aircraft are flown
in close proximity to airports. As such, the AMA Safety Code advises modelers to remain at or
below 400' AGL when within 3 miles of an airport. AMA believes this meets the intent of the
Advisory Circular in creating a means by which model airplanes can operate in a safe and
cooperative manner without imposing an undue restriction on the modeling community.
Moreover, model aviation’s impeccable safety record over the past 28 years has proven this to be
the case.
AMA's experience has shown that the risk posed by model aviation diminishes significantly at
distances greater than 3 miles and any remaining risk can be mitigated almost entirely by proper
safety training and the modeler’s ability to see and avoid the manned aircraft when a conflict
exists. This has been AMA's position since the AC was published in June, 1981, and this is
AMA's position going forward.
That having been said, there are some unique aeromodeling activities such as thermal soaring
and Free Flight where additional risks do exist due to the nature of the operations. In these
incidences AMA is considering additional means for mitigating the risks while essentially
allowing the modelers to continue to enjoy these activities. We will work directly with the
modelers, the Special Interest Groups and the FAA in developing these procedures. Once the
concepts are developed and put forward for consideration more information will be made
available through the AMA web site.
Though there are as yet no guarantees, AMA is confident we will be able to work through these
issues, resolve any remaining concerns and ultimately provide a safe and effective program that
allows the modelers to continue to enjoy the hobby in much the same way as they have in the
past.

Regards
Frank