Well here it is. The day that both Facebook and Zynga have been dreading. Yesterday the two were officially named as defendants in a federal class action lawsuit.

Filed by Kershaw, Cutter & Ratinoff, a Sacramento firm that specializes in class action lawsuits, in Northern California yesterday, the complaint is seeking damages upwards of $5 million. The issue in question? Well, if you’ve not been following TechCrunch’s ongoing series on the ScamVille affair, it’s best to just head on over and give it all a healthy read right now. Kershaw, Cutter & Ratinoff have been seeking out those that were subject to a number of unauthorized charges emanating from currency offers via social games including Mafia Wars and FarmVille.

Now here’s where things get interesting – neither Facebook nor Zynga actually produce(d) the offers themselves, but rather simply sold advertising space to external ad providers. At it’s most basic, we’re looking at a revenue sharing program here, and reportedly both firms have made heaps of cash from said offers. Apparently, Zynga garners almost a third of it’s revenues from these offers, something that Kershaw, Cutter & Ratinoff have exemplified in their filing.

And to make matters worse, Zynga CEO and founder Mark Pincus has been fimed stating, “I did every horrible thing in the book just to get revenues.” Ouch. A judge certainly isn’t going to take kindly to such statements.

Valleywag has the entire complaint here – if you’re so inclined to read legalese.

And while a number of pundits are quick to point out that this recent filing has got to have investors quaking in their boots, it flies directly in the face of Zynga’s announcement earlier this week that it had acquired another $15 million in VC funding. Bad timing? If it is – that’s gotta be one of the worst calendar mis-schedules we’re seen in the Valley in a long time.