[austinjp]

Is there any detailed opinion on good and bad approaches to this problem? It is clearly a hot topic.

I'm sure each product listed conforms to one from a small set of design patterns. Has any credible analysis of these designs been published? Are competing offerings likely to evolve toward a stable converged solution? Or is there something in this problem that remains fundamentally unsolved?

I appreciate it's turtles all the way down, but I'm wondering if anyone has proven the merits of some approaches over others, or components within the approaches at least.