A question came up this summer about who can log PIC time when flying as a safety pilot. There’s a nice clarification of those rules (and lots of other rules) in the FAA’s Nov/Dec safety briefing this year: https://www.faa.gov/news/safety_briefing/2016/media/NovDec2016.pdf.
Here’s the relevant text:
The safety pilot is required to hold at least a private pilot certificate, be rated for the category and class of airplane to be flown, and hold a current medical as required by § 61.3(c). If the safety pilot is acting as PIC for the simulated instrument portion of the flight, the safety pilot may log that time as PIC time under § 61.51(e)(1)(iii) because he is acting as PIC of an aircraft for which more than one pilot is required under the regulations. The PF [pilot flying] may also log the time as PIC time under § 61.51(e)(1)(i) as the sole manipulator of the controls of an aircraft for which the pilot is rated. Additionally, the pilot flying under simulated instruments may log simulated instrument time. However, if the PF is acting as PIC and is the sole manipulator of the controls during the simulated instrument portion of the flight, then the safety pilot may log that time as second in command (SIC) time because he or she holds the appropriate category and class ratings for the aircraft being flown and more than one pilot is required under the regulations under which the flight is being conducted in accordance with § 61.51(f)(2). This is further explained by a legal interpretation in 2012 (Trussell) http://go.usa.gov/xk4bB.