Joining and locking down the account by disabling all the notifications would make them stop spamming you. Dunno what's more important to you, getting rid of the spam, or the principle of not having an account there?
How about a class action lawsuit for unsolicited spam and data scrapping?
Much longer to wait for results but much more satisfying.
Would an invite to gmail by a friend be considered spam?
Nor is this "data scrapping[sic]" you mention anything of the sort if your friends deliberately requested, or passively acquiesced, to Facebook reading their address books.