Some interesting points everyone.

@Dave Milligan: Wow, I did not know that!
@Javier: I can see your point about import restrictions etc. Different countries have vastly different import restrictions, so I imagine one could choose the least restrictive country in the region to fly in to and then ride from there. I know of one XR250 in Burma that was brought in piece by piece and reassembled.
@Pecha72. Yes, I was thinking about the dangerous goods problem as well. That's why I mentioned my camp stove. But when I took it apart into it's component pieces, they no longer considered it a camp stove. Just "camp stove parts". I understand that even for normally crated and air-freighted motorcycles, you sometimes need a "dangerous goods" inspection, so either way you'll need to go through it. I guess as a last resort one could ship engine and gas tank separately.
As far as disassembling and assembling... I'm thinking of something like my XR250. Pretty simple. Probably 5-6 hrs at each end.
I'm also thinking that in some places, dangerous goods regulations etc. may not be enforced as strictly.
@BCK_973 Yes, I guess boxes could go missing... don't know what the statistics on that are. 1 in 10, 100, 1000, 10000? I'd be ok with 1 in 100 risk and my guess that for many destinations it's lower than that. And you could insure too.