Vint Cerf is making noises that IDN is a huge technical challenge:

“One of the most important aspects is for the user to make unambiguous references to every registered domain name.

“Historically this has been through a small subset of Latin characters.”

[…]

Mr Cerf said that in order for other scripts to be introduced into the domain name system, there needed to be rigorous testing to ensure that users could be certain they will reach their online destination no matter which script they used.

“Domain names are not general natural language expressions. They are simply identifiers,” he said. “They must be unique. Names registered today must be able to work into their distant future no matter what characters are added.”

He warned: “A miss-step could easily and permanently break the internet into non-interoperable components.”

I respect Cerf but this seems like fear-mongering (perhaps to counter international pressures particularly on ICANN, which is today controlled by the USA) rather than a technical argument. Uniqueness of names can be guaranteed in IDN, and talk of “permanent” break of the Internet into non-interoperable components, is a bit irresponsible. Also, phishing/spoofing attacks (the concern brought up above regarding the certainty of users in accessing sites) are not unique to IDN and have been addressed both before and also within IDN. Wikipedia offers a decent introduction to IDN/IDNA that addresses many of these points, and provides information on IDNA support in applications (e.g: Mozilla/Gecko).

The opinion of Viviane Reding of the EC, quoted in the same article, are, I think, a bit more on target:

Viviane Reding, the EC’s information society commissioner, said: “Bridging the digital divide is not just a matter of screens and cables.

“It is equally important to recognise the extent and value of cultural diversity within global village of the internet. That is why multilingualism is important.”

She said that IDN was “sometimes wrongly seen as technical issue”.

“There is legitimate political imperative,” she said. “Users want to be able to use Chinese ideograms and Arabic scripts.

“There is a real danger that a prolonged delay in the introduction of IDN could lead to fragmentation of the internet name space.”

I cannot but draw parallels to the (oft-mentioned) doomsday protestations of car manufacturers regarding everything from seat belts to better mileage.