The machines are privately developed, and their software is kept secret. There's increasing doubt about their integrity - their vulnerability to hackers, whether they've already been hacked by the time they're delivered, whether there's a rogue WiFi chip lurking within, for example.
Advocates of IRV and choice voting, don't be fooled when the vendor calls its equipment "compatible." There is no machine in the United States that will, on delivery, let you run an election with ranked ballots. Cambridge uses modified machines. San Francisco spent extra money for machines that handle ballots with space for only three rankings. Burlington uses machines to count first choices; if there's no majority in round one, begin the hand-count.
You can patch these machines to support ranked ballots. Without a promise from the company in the initial contract, though, the patch can be pricey - and there's no incentive to deliver. Even if the vendor delivers, transparency issues remain.
With entry barriers like this, you'd think ranked voting systems were alien. But these entry barriers are specific to the American equipment industry. Scotland's 2007 elections will use choice voting (a.k.a. STV, or the single transferable vote) with an electronic count. Voters mark ballot papers, which are fed into a machine for counting.
Australians have come up with a solution that ensures transparency and cost-effectiveness: open-source counting software used on old PCs running Linux. It's been used in the Capital Territory (where Canberra is) since 2001. Computers-as-voting machines are wired to a server computer that administers the election. There's no WiFi involved.
Although a private Australian company designed the system, it was based on specifications set by independent election officials, who posted the code on the Internet for all to see and evaluate. What's more, it was accomplished from concept to product in six months. It went through a trial run in a state election in 2001. CNET News:
"I wouldn't go so far as to say that open-source e-voting is key to the democratic process, but I do believe that one of the key features of a democratic electoral system is transparency--essentially being able to externally verify that what goes in is what comes out," said Phillip Green, electoral commissioner for the Australian Capital Territory. "Open-source e-voting software is one way of achieving transparency, but not the only way."
One college student was beefing eVACS (electronic Voting and Counting System) up to U.S. standards for inclusion in all our non-supporting equipment. It'd be interesting to see how far that got.
For now, eVACS is a solution for larger private groups who want to run elections under IRV or choice voting with fractional transfer.
It just goes to show that transparent elections run under fairer systems aren't impossible to hold.