Chris Keith just Jesus-Blogged on "early ambiguous christology" in a post titled, Maybe Mark Knew What He Was Doing. It's a brilliant triangulation that speaks well for itself, so I'll just add my two bits here.
I've been thinking for a while about some sweet old women and crotchety old men (and vice versa) in the early Jewish-Christian community - maybe lots of them or maybe just a few individuals - whose traditional sensitivities Mark was trying to protect. It just wasn't necessary to both blow their minds AND piss them off.
By the same token, being explicit would have been strategically unwise, embroiling the text in controversy unnecessarily. If theological understanding of these things was not yet uniform, Mark had no way to say these things *without* being ambiguous. It's actually the textbook situation for political metaphor (Faerie Queene) and stable irony (A Modest Proposal); how does one speak the unspeakable?
Given that Mark is the earliest Gospel, we should have been surprised if this were different.
Great post, Chris. Brilliant as always.