After careful reading of Sacca, Conway, and Arrington, I've come to the conclusion that they might all be correct in their representation.
We know there were at least two meetings of the "Super Angels" - It's possible (likely) that the first meeting that Sacca attend was an aboveboard engagement in which all of the positive conversations that took place were as Sacca described it. Indeed, I read Sacca's email as a shout-out to Conway saying "Hey - the meeting I attended, was above board - don't paint me with the second meeting brush"
It sounds like in the second meeting, the conversation departed from "How do we help entrepreneurs" and started sliding into "How do we increase value for angels". Maybe not full out (actionable) collusion in which any agreements were made (and the concept of agreement is pretty important in collusion) - but skirting dangerously close.
David Lee was at that second meeting (and, for all we know, was one of Arrington's sources - He had Three), likely gave conway the briefing, and conway, being savvy, realized he needed to immediately separate himself, particularly as all this email floating around is discoverable.
Nobody should, for a second, think that Ron Conway is writing email with the belief that it won't be seen in the public light.
Talking as a group about things like holding down valuations, dealing with YC leverage, and the impact of convertible notes on the Angel's cut of deals is all pretty dangerous territory. Sacca wasn't at the second meeting, so his email has to be taken in that context.
All in all I think Arrington has done a great service with some excellent blogging, not only to the startup/entrepreneur scene, but also, ironically, to the Super Angels themselves. By surfacing these conversations early on, I'm of the belief that he may have actually given them a wakeup call before they started doing (illegal?) things like agreeing as a group not to accept convertible notes.
This is hard hitting reporting that harkens back to a day of serious reporting - ironically done not by a "mainstream" news outlet like the WSJ, or NYT - but by a "mere" blogger.
kudos.