Is a floating pin equivalent to a very weak pull down?
Have recently been characterizing an input pin on a PIC microcontroller. The pin can be alternately set to CMOS in/out, Schmitt input, or analog input. When set for Schmitt input:


Data sheet specification of leakage current is +/- 5 nA.
Measured leakage current at room temperature is less than 3 pA.


Similar results were measured years ago on a different PIC microcontroller. Be aware that leakage current is very temperature-dependent, and can be in either direction. So you cannot assume that it floats to a logic low state. 
It is possible that electric field of a hand-waving over a floating pin can change its logic state.