Hey Jensen, I see them as autonomus from each other. Seperate successful entities - so to speak.

I use both everyday.
Most people are honest about their real name on face book and many of their friends are people they know.

Whilst tribe has a completely different aspect that facebook doesen't really succeed in.
Strong consistant forums.

Personally I've learned a lot of valuable information on tribe.

Plenty of tribers like to be anonymus as well.
I use tribe for many online friends who I've never met and facebook to keep in touch with various real friends around the globe..

but that's just my 5cents worth..
Wonder if anyone else will have an opinion..

Tribe doesen't have a strong presence in Australia and I prefer it that way.