As the tech industry said goodbye to visionary innovator Steve Jobs Wednesday, two other larger-than-life Silicon Valley personalities started a new public tiff.

At Oracle OpenWorld in San Francisco Wednesday, Larry Ellison completed what InformationWeek's Charles Babcock describes as a 180-degree turnaround on cloud. Ellison announced that Oracle data centers will soon provide infrastructure as a service (IaaS) for customers who wish to develop Java applications or deploy the new Oracle Fusion applications in a public cloud setting.

Meanwhile, former Ellison protege Marc Benioff staged a hastily arranged offsite "keynote" Wednesday near the Moscone Center--after Larry Ellison unceremoniously dumped him from the Oracle Open World lineup, reportedly over a derogatory Facebook post.

Benioff made his case to his faithful, who had been gathered up in the street and via social media postings: Multi-tenant computing is "more reliable, more secure, and more available. It's the future. Single tenancy goes hand-in-hand with selling proprietary mainframes," Benioff said. As Babcock notes "In case anyone was wondering what he meant, he also referred to Oracle "Exadata mainframes."

At the same time Wednesday, cloud luminaries gathered at Interop New York debated Benioff's self-proclaimed nemesis, the private cloud. Salesforce's party line, of course, continues to be "beware the false cloud." Or as Peter Coffee, Salesforce's director of platform research, put it to an Interop panel Wednesday, buying into private cloud equals buying into "wildly over provisioned capacity that's rarely used."

I understand why Salesforce continues to push this "private cloud is a false cloud" line, but I don't agree--and I'm wondering when Benioff's customers will start to tire of it. Too many innovative enterprise CIOs have already invested too much time and energy in the private cloud model--and reaped too many rewards--for us to be still debating whether a private cloud is really a cloud at all.

Does Marc Benioff really want to tell CIOs like FedEx's Rob Carter--who recently shared how he has overhauled his vision for data centers, featuring private cloud--that private cloud is a crazy strategy? Carter, by the way, made a point of telling attendees at our recent InformationWeek 500 conference that he likes that when he looks at Salesforce data centers, he sees data centers that look very much like his own. But for now, his cloud road is private.

Of the many enterprise CIOs at our recent InformationWeek 500 conference with whom I talked cloud, almost all of them using cloud use a mixed private and public cloud model. Not one told me private cloud was bunk.

That's one reason why it's always intriguing to hear both sides for and against the use of the private cloud model go at it, as they did in the Wednesday Interop panel "Great Debate: Will We Always Have Private Clouds?," moderated by Alistair Croll, founder of Bitcurrent.

"Private cloud is an oxymoron," declared Peter Magnusson, engineering director for Google. "It's just another word for on-premise system or mainframe or servers. That's not a cloud." Clouds are at their essence multi-tenant, ideally massively multi-tenant, Magnusson said.

"Microsoft themselves see their private cloud offering as a transition step," Coffee said, referencing Microsoft's Tuesday Interop keynote, in which the company told attendees private cloud will be 10 times more expensive than public. "It's not a plan," Coffee said. "It's just a stage."

Ian Rae, CEO of CloudOps, fought for the opposite point of view: "Our colleagues are trying to argue the public cloud can do anything," he said. "There's going to be certain workloads which just don't make sense." The debate, Rae said, "should be about what is the right balance," between public and private cloud in your enterprise.

Exactly.

At what point does Benioff denying private cloud start to sound like Microsoft denying Google Apps?

Croll asked the Interop panelists, "How long until we think of private clouds as mainframes: old, evil and hiding in the basement?"

My bet is, it's going to be quite a while.

Laurianne McLaughlin is editor-in-chief for InformationWeek.com. Follow her on Twitter at @lmclaughlin.

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