I don't think anyone is seriously calling the IM messages phony.
Simple common sense, again. If phony, why did Foley dive off the plank almost immediately?
I have seen no evidence, either in how the messages were formatted or anything else, to imply that the original IM messages (separate issue from the e-mails) were fake.
I have seen evidence that they were acquired somehow and dispersed for political reasons, long after the fact, probably using a blog constructed specifically for this single purpose.
