What about property owner permission? I feel like that's something really important. Even if I'm not at my house I should still have a say if someone wants to fly some 50 lb contraption over it.
And if any of the regs in part 91 end up applying-
FAR 91.13 (a) just says aircraft have to be operated safely. "No person may operate an aircraft in a careless or reckless manner so as to endanger the life or property of another." So unless they were buzzing your house that might be hard to prove.
The regs are loose around dropping items, too- FAR 91.15 [1]. They don't talk about needing property owner permission or anything. Maybe you could twist that in your defense since it is so loose- if something did fall from a UAV.
[0] http://en.wikipedia.org/wiki/Airspace_class_%28United_States...
[1] http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf...
[1] http://www.flightsimaviation.com/data/FARS/part_91-119.html