In case of a drone strike with an airplane below 400 feet, who is at fault? If a plane is flying VFR (see and avoid) below 400 ft, and the pilot collides with a drone due to not seeing the drone until it's too late to take evasive action, then would the pilot be at-fault for insurance purposes? Would the drone operator (or the pilot) have violated any federal regulations for not keeping clear of the other craft?

Conditions:-


Class E or G airspace
out of the 5nm radius of an airport
sparsely populated area
operator of drone is not within 500 ft of where the collision occurred (i.e. for the purposes of FAR 91.119 (c)).
I have a smaller piston engine plane in mind, but I'm assuming that the outcome would be the same for faster jet aircraft too
The FAA has some rules pending about this, you can read them here but for drones under 55 LBS one of the proposed rules is, 


  Must yield right-of-way to other aircraft, manned or unmanned.


and since you bring up class E it should be noted that 


  Operations in Class B, C, D and E airspace are
  allowed with the required ATC permission.


if/when this goes through it looks like its the drone operators fault since the plane had the right of way 

According to the FAA's website in relation to model aircraft they state that, 


  (4) the aircraft is operated in a manner that does not interfere with and gives way to any manned aircraft;


this is pretty much a blanket statement that maned aircraft have the right of way but the FAA handles most things on a case by cases basis so in the end of the day it could go either way.