I was also skeptical when I first saw the news articles (like this one) that said that RSA had published a statement where they supposedly refuted the existence of that NSA deal. The existence of the deal was originally broken by Reuters in this article, where they cite "two sources familiar with the contract" as their sources. But then, after more in-depth analysis of the RSA blog post where they supposedly "denied" the existence of the deal, it was revealed that actually RSA neither denied nor acknowledged that such deal existed in their statement. They are just using general wording to give an impression, that they would certainly never do such thing. But they are not directly denying the existence of the deal.
Now, thinking logically, it's pretty damn clear that they would have denied that such a deal was ever made, if they were in the position of making such a claim. But given they don't directly deny the claims presented by Reuters, it would seem a much more logical explanation that the deal indeed was made, and RSA just went into damage control mode after the publication of the Reuters article. Lying to the public would have meant more damage if Reuters would have later been able to present the actual paper of the deal, so I suppose we can take their lack of directly denying this deal's existence as an admission of sorts. This is also the reason why speakers are canceling their appearance in the conference ("Your company has issued a statement on the topic, but you have not denied this particular claim.")
So, I think we have grounds to believe that there is actually quite much truth to the original story by Reuters. As they say, the deal was "handled by business leaders rather than pure technologists". I am pretty sure that this is a yet-another example of a major manager-level f*ck up. Tech companies very often have all the expertise on the technical personnel level, while managers are a "necessary evil" who often have much fewer insight into the technical field where the company actually operates. Of course, anyone with even the slightest idea of how the IT security field functions, would never ever endanger their company's credibility (at least for such little reward as $10 million), because deals like this tend resurface in the public sphere sooner or later. All we can assume that someone in the management made a very major f*ck-up and made this secret deal with NSA without much consulting from the technical folks. But I am pretty sure that now that this deal has surfaced in the public sphere, it will end up costing RSA a great deal more in lost sales than what the "business leaders" anticipated they could gain in short term from making the deal with NSA.