What would a survey of a cross-section of "computer experts" have looked like predicting the Internet in 2005 from 1990? The level of awareness required to make that prediction accurately is not generally found, people who did understand it well enough to make an educated guess would be modeled as outliers. The above survey is asking people to make a similar type of prediction.
An important aspect of AI predictions like the above is that it is asking people who do not understand how AI works. They are definitely experts on the history of past attempts but that does not imply the domain knowledge required to predict human-level AI. It is a bit like asking the Montgolfier brothers to predict when man would land on the moon -- experts on what has been done but not on what is required.
There are many reasoned extrapolations of technology arrival dates based on discernible trends -- think Moore's Law -- but something comparable in AI does not exist. The vast majority of AI people have no basis on which to assert the problem, something they generally can't define, will be solved next week or next century. The few that might know something will be buried in the noise floor. Consequently, I do not find much values in these group predictions.
Zeitgeist is not predictive except perhaps in a meta way.
The survey gives a 33% chance of an "extremely bad outcome" from the development of machine intelligence.
Another of their surveys gave a 5% chance of human extinction at the hands of superintelligence by 2100.
These figures may need to be "adjusted" - on the grounds that the FHI seems to be a bit of a doom-mongering organisation for whom the end of the world is a fund-raising and marketing tool, and the surveys sample from their friends and associates.
Link: Machine Intelligence Survey (PDF)