Picked this story from the OpenStreetMap IRC room – it’s is this very well written blog post by Rich about his thorny experiences in Uganda collecting data for OpenStreetMap.
http://blog.wonderfullyrich.net/2010/01/uganda-treats-you-right
At the time I thought it was ludicrous that they would suspect a white umuzungu as a terrorist, especially one with such as bad cover story that it took hours to explain what openstreetmaps was, that it was a volunteer activity, and that my reasons for doing this was primarily altruistic and maybe I can make money off selling it later
In keeping with some earlier posts:
Indian Nokia map collectors imprisioned
Mapping as a Terrorist Activity
thinkwhere 
Scarey stuff.
I guess carrying a copy of your passport would help in that situation. Also I suppose some official looking leaflets explaining OpenStreetMap would be useful.
Reminds me slightly of Firefishy’s old encounter with some special embassy police here in the U.K. ( a while ago now http://www.openstreetmap.org/user/Harry%20Wood/diary/5960 ) I remember he said they were confused and deeply suspicious that he had no business cards related to his mapping activity.
iam sorry, i didn’t got u …