I heard this a few weeks ago... sucks for anyone caught!
what they are doing is offering you to pay a settlement charge, probably like $10 or $20 bucks... knowing that industry, they probably want $100. They are smart and know people will pay not to get in trouble and probably 50% if not more will shell out the cash.
if you dont pay, then they will then pursue legal action on you. IMO, i call bullshit. they have no way to provide evidence that you downloaded the movie, even if the file was called "the hurtlocker full movie that is pirated and you can watch on your PC even tho it is in the theaters.avi" UNLESS they take your computer
personally, i would take the settlement and write back to them and say bullshit, i didnt download your movie nor do I download any illegal content.