I think it's funny that people are freaking out on HN about this. The hacks at Defcon all took a long time to do, and I believe all required keys to the machines, and all were done on older voting machines. There has been no evidence of people hacking machines during the elections. Stuffing ballot boxes and other forms of voting fraud have been around for a long time, and nothing we do is going to stop it 100%.
Also voting machines generally have paper copies that print off the back of the machine that are anonymized but can be matched if foul play is called into question, at least in my area. Couple that with monitors that stand near machines or walk around and I feel pretty comfortable with electronic voting.
The only plausible hack would be an inside job, but I too find this difficult to believe. It would takes tons and tons of people to hack the machines if it required physical access. You'd have to hack ever machine, and even when you were done there are so many districts it would be nearly impossible to swing the election in any meaningful way.