Errata: fixed issues regarding 3Tera and CohesiveFT, both of which deserved better positioning in the stack than my cloudy thoughts had heretofore imagined.
Again, many thanks to vendors who are contacting me, and kudos in general to discussions on the "cloud-computing" group.
One thing jumps out from this diagram now: items 6 and 12 are placeholders. What vendors or projects might emerge to cover them? For example, might some enterprising soul rewrite portions of the Scalr project so that it can handle APIs for other vendors?