...they're also competing with a nearly infinite supply of free, amateur videos from countless user-generated sites
e.g. youporn.com
Consumption of porn is recession proof. The business of professional porn generation is not. Like other produced content, it is suffering from democratized tools of generation and dissemination.
It might be recession resistant but many of the mainstream porn companies are having trouble right now because of increased competition and also because of the huge amount of free content that can be found on the web via these tube sites.