Wow

It will take a couple thousand hours to burn a petabyte disk if current DVD burn speeds can be used as basis for comparison.

I suspect that the RIAA members will find a way to make a regular 120 minute movie require 1PB of disk for retail sale though!

The source funding to bring the tech to market is pretty obvious.

Decades away

I like how Nik implies that it will obsolete Blu-ray. This tech is decades (if not further) away.

most of these silly press releases are to secure funding, nothing else. The fact that some people get sucked in by it all, says alot about these people.

millimeters

Seeing as though a CD or a DVD is already something quite fragile...protection technology would have to greatly increase if such high volumes of data are to be placed on a single disc.
A minor crack on a microscopic level could potentially ruin several petabytes of data.
Regardless of what your data is, you would not want petabytes of it damaged. Most people do not even know how much information that is...so lets just say its a really long number...long enough to want to have it intact.

Perhaps a special casing such as the old magneto optical discs?