I found an interesting article which goes to show that if anything is unsafe it's artificially low speeds. I have always had to explain to people that the cause of accidents is driver distraction, not higher speeds. Another interesting thing is that even with all of the added driver distractions in cars nowadays (cell phones, nav sys, touch screens etc) fatalities are still down overall with the higher speed limits now.
http://www.opinionjournal.com/editorial/feature.html?id=110008621
http://www.opinionjournal.com/editorial/feature.html?id=110008621