I think we should play on his home turf and not expect him to come to ours.
I don't even remotely "expect" him to come here.
I do know, that if I was doing research into a subject I was new to and was offered an invite onto my subject's forum, I'd be delighted at the opportunity to do that.
He doesn't have to respond to an invite, he is completely free to say no thanks, he may well have plently of stuff from his own blog or other communications (facebook etc).
Are there any specific PR rules or precedents for such invites, or do people just sign up of their own accord if they want ?
It was eafw's suggestion to have the discussion in a member only area, unless I misunderstood.
Yes, because it's the internet equivalent of inviting someone round to the local group meeting for a chat - off the record. There are people out there who would sabotage any effort by the media to stray from the usual line remember.