According to Forbes and several other sources, Nvidia has had it's internal network breached. Currently, the breach appears to be limited to usernames and passwords for the Nvidia internal network.
The way in which this hack was executed -- and the timing, at Christmas when the sysadmins were busy with other things -- suggests this was a well-planned and thought-out attack, rather than an opportunistic one. The original source was allegedly a staff member whose system was compromised and subsequently used as an attack vector.
Nvidia has gone on record, via an internal email sent to employees after the breach was found, stating that there is "no indication other data." Sources have also stated that the breach has been ongoing since the first week of December.
What is particularly interesting about this hack, at least to this writer, is that Nvidia isn't a standard target for crackers. There is much lower-hanging fruit to be taken from other sites that have more credit card and user details.
What may potentially be more interesting is the fact that Nvida makes advanced silicon for supercomputers and advanced, sometimes classified, simulations. (Not to mention enthusiast-class GPU IP.)
Machines such as Titan (pictured) are the latest generation of supercomputers, and the information on it is worth a lot of money to the right party. There has, as yet, been no confirmation of any intellectual property, classified or otherwise, being copied from the network.