I don't see any evidence being provided for the Facebook platform being used to help spammers, other than anecdotal evidence of people changing their login credentials and still being seen to send spam.
I think it would be interesting if it were shown that opening the platform directly led to exploits being used for spam, but this article doesn't seem to have any actual evidence. It's entirely speculative.
I remember when MySpace first started getting really spammy. If the consumers have moved to Facebook, eventually the spammers will figure out a way to follow. Check out this BBC piece on the ease of creating a phishing application: http://news.bbc.co.uk/2/hi/programmes/click_online/7375772.s...