So, first, read this sub-thread [0] for a bit of history.

Second, here [1] is a summary of the guidelines from the AMA.

Third, the full FAA rule can be viewed here [2] (PDF warning).

[0] https://news.ycombinator.com/item?id=10733635

[1] http://amablog.modelaircraft.org/amagov/2015/12/14/ama-and-t...

[2] http://www.faa.gov/news/updates/media/20151213_IFR.pdf