After the Instagram debacle, where it changed its terms of service to give itself greater rights over user photos and reversed itself after a user backlash, it's worth thinking about the security threat stemming from terms of service in general.
As cloud computing becomes the norm, as Internet security becomes more feudal, these terms of service agreements define what our service providers can do, both with the data we post and with the information they gather about how we use their service. The agreements are very one-sided -- most of the time, we're not even paying customers of these providers -- and can change without warning. And, of course, none of us ever read them.
Here's one example. Prezi is a really cool presentation system. While you can run presentations locally, it's basically cloud-based. Earlier this year, I was at a CISO Summit in Prague, and one of the roundtable discussions centered around services like Prezi. CISOs were worried that sensitive company information was leaking out of the company and being stored insecurely in the cloud. My guess is that they would have been much more worried if they read Prezi's terms of use:
With respect to Public User Content, you hereby do and shall grant to Prezi (and its successors, assigns, and third party service providers) a worldwide, non-exclusive, perpetual, irrevocable, royalty-free, fully paid, sublicensable, and transferable license to use, reproduce, modify, create derivative works from, distribute, publicly display, publicly perform, and otherwise exploit the content on and in connection with the manufacture, sale, promotion, marketing and distribution of products sold on, or in association with, the Service, or for purposes of providing you with the Service and promoting the same, in any medium and by any means currently existing or yet to be devised.
With respect to Private User Content, you hereby do and shall grant to Prezi (and its successors, assigns, and third party service providers) a worldwide, non-exclusive, perpetual, irrevocable, royalty-free, fully paid, sublicensable, and transferable license to use, reproduce, modify, create derivative works from, distribute, publicly display, publicly perform, and otherwise exploit the content solely for purposes of providing you with the Service.
Those paragraphs sure sound like Prezi can do anything it wants, including start a competing business, with any presentation I post to its site. (Note that Prezi's human readable -- but not legally correct -- terms of use document makes no mention of this.) Yes, I know Prezi doesn't currently intend to do that, but things change, companies fail, assets get bought, and what matters in the end is what the agreement says.
I don't mean to pick on Prezi; it's just an example. How many other of these Trojan horses are hiding in commonly used cloud provider agreements: both from providers that companies decide to use as a matter of policy, and providers that company employees use in violation of policy, for reasons of convenience?