We run into this at my work. We provide a front end that insurance companies log into. We get a ton of false positives, and sometimes it is a random auto selected content setting or just for no apparent reason at all.
There is this sort of random half-joke half-rumor that the browser makers are going to start making us pay a fee to be "secure" and "well-known" and "safe" on their browser. On some of the stuff I've seen in alpha and beta testing it wouldn't surprise me a bit if we were headed down this road. I think a whole new round of browser wars are coming. Of course on the flip-side, we are just putting a lot more time toward developing our own apps for our customers to use that are free, and then they don't have to deal with any of that business. They download it from us, we control the back end, so they know that's secure, and we control log-ins, so that's secure, and we control the program in which the "workgroup" (can't give too much away here) that is receiving the data uses and all interactions. The web side of it just makes it easier, but we can bypass it entirely, but I find myself spending an inordinate amount of time going back through really specific processes that a big customer has dealt with for a day or two, only to find out it's just nothing and they're getting a false positive (or a negative, however you want to look at it).
We have NO outside advertising of any sort and are used by professionals in the industry to process claims, so it wouldn't even be some piece of bad linkage causing the problem. It's an irritant, but we usually figure it out within 15-20 minutes. It's the increased frequency that is the problem, and then I have to be a jerk and tell the president of a major company (well I don't, but the contact at my company who has me run through everything in the product does using my steps of reproduction and my workaround) that "we are very sorry, but this is why we only support IE 7,8, and 9 (barrrrrf), and don't provide support if you are using Chrome, Firefox or anything else (that works ten times better). Have a good day!