First let me state - they are legitimate products made by Nikon or Canon.
They have not entered the US through Nikon or Canon distribution channel.

I don't know if their is a comparable website for Canon and other manufacturers but for Nikon users:

Nikon has long used the first digit of the serial number to indicate region for many of their products:

1-Not used
2-Japan
3-USA
4-Europe (excluding UK)
5-Canada
6-Australia/New Zealand
7-Asia (excluding Japan)
8-United Kingdom
9-Not used

Nikon users can go here to check on lens serial numbers:

http://www.photosynthesis.co.nz/nikon/serialno.html


If you buy at a place like B&H they will provide the manufacturers warranty however Nikon and Canon usually will not honor the warranty for gray market except for special cases like the Nikon D600 shutter which you can take any D600(even used and out of warranty) to any service center in the world and they will fix it.

http://www.bhphotovideo.com/find/HelpCenter/USGrey.jsp

I am a real estate photographer. I set the exposure for the windows and add flashes to expose the interior. Sometimes I have to layer the shots to get a good view out the window. I don't use HDR because it does not look as nice or realistic.

I use dropbox to share the photos with my clients.

Here is one I just shot yesterday. I used no HDR and no layering in any of these shots.
This is another shoot that was the most difficult I have done because the house was decorated in very dark colors and I had to pull out all my flashes to light it.
http://www.dropbox.com/sh/o95iwlavsk2yvf4/AAALUxYCq234VsSE5xLTtwgoa