I worked on an embedded system that aggressively cached images in memory dedicated to the GPU. It wasn't uncommon for gl texture allocation errors to occur - and in addition to that, we needed to decompress images packed in various formats into whatever format the GPU supported (typically from png to rgba32). In low memory situations, it also wasn't uncommon to not have enough contiguous memory to perform that decompression - in which case malloc would fail.

Gotta love putting forth every effort in software to keep the BOM down :)