Tesla Motors has pushed Panasonic beyond its production limits.

In response to demand for lithium-ion battery cells (most of that demand coming directly from Tesla), Panasonic will invest $204 million by March 2014 to increase battery cell production for the automotive sector.

Panasonic will use some of that money to construct an additional cell manufacturing line at its facility in Osaka, Japan.  Additionally, Panasonic will re-fire an idled line at is Osaka site.

Panasonic calls this a "necessary investment."  For Tesla, these Panasonic cells are necessary and more will certainly be needed when that affordable Gen III Tesla arrives.