With respects to their choice to take that road as they did, my first reaction was that they didn't do their research, and that it was a silly, high risk move. If I am not mistaken, even the Lonely Planet warns of this specific stretch of road.

I had a poke around the blog of one of the people involved at it turns out they they had attempted to research whether their security concerns were still valid and felt that it had been a couple of years since since the last robbery report. The rider in question, without the pillion, travelled the road a couple of weeks prior without incident.

2014 Travels <-blog

Having spent New Years on Lake Atitlán, we were told later that the road we took back to the main highway, which wasn't the direct route, was also "dangerous", which is to say, we travellers probably end up on more high risk roads than we realize. To me, this road seemed to have too much car traffic to be of serious concern, but surely something must have happened at some point.

With respects to not loosing your valuables, I try to think about the spectrum of security versus convenience, and that you don't really get to have both at the same time.

In Salento, Colombia we "narrowly missed" be victims of robbery via knife point. Several hours having already returned to where we were staying, four other guests were accosted by four young men in balaclavas wielding kitchen knives. The "victims" (no one was hurt) received full pat downs, and how they explained it, it would have been pretty hard to conceal any item, including money belts, etc.

From our understanding, this robbery was very rare for the area, being a quaint rural town, and local people were genuinely embarrassed by the act. Police presence increased immediately. As it turns out, even in "safe", moderate traffic areas there are opportunists.