Continuing the discussion from Hunt's 2007 Critique of Axe:
As for the simplest cell? We should expect that the first cell was far more simple than anything we find today, which has accumulated a lot of interlocking complexity (like Rube-Goldberg machine) by the Mullerian Two-Step.
For this reason, Venter’s group is not determining the simplest organism possible. In extant organism, that would likely be viruses. In the distant past, we have no clear idea at all of how simple or complex that first cell might have been.