On Android, you are lucky if Google deems a bug worthy of fixing.
I'm a member of Google's Android security team, and I want to correct this. The only component in which Google doesn't fix bugs is the old Webview implementation. I'm not going to try to explain or defend that decision, just note that at this point we think it's more productive to get apps to stop using it to display untrusted content on pre-4.4 Android. Outside of that, Google does provide fixes to all significant issues that are reported to us, and we provide those fixes to device manufacturers, at no cost and with security bulletins explaining the nature and severity of the issues. Further there are partnership policies in place that require manufacturers to release updates for severe issues. The nature and scope of those requirements aren't what I wish they were, but Google's ability to dictate to Android OEMs is limited (which isn't a bad thing, though arguably it is in this case).
The best sandboxing is useless if the OS itself has known and remote exploitable security issues, as Android usually does.
The first portion of this sentence is indisputably true. The claim that Android usually has remote exploitable security issues, not so much. Local exploits are pretty common, as they are on every platform, frankly. Securing against local exploits is a hard problem, though I think we're making significant progress. We're finding that SELinux is making many vulnerabilities non-functional on 5.0 and above (granted that it will be a couple of years before 5.0+ represents the majority of Android devices). Functional remote root exploits, however, aren't actually that common, even on pre-5.0 devices. Also, such high-severity vulnerabilities generally *do* motivate manufacturers to deploy fixes (again, pre-4.4 Webview being the notable exception).
Also, I'll point out that thanks to the Android Verify Apps tool, which is active on several hundred million devices, Google has very good insight into exactly what (known) vulnerabilities exist on real-world devices, and even quite a bit about how often exploits are used (though that data is more squishy and speculative). This data even covers a lot of devices that don't use Google Play, since the Verify Apps opt-in is offered to all devices, not just those that use Play.
I can't provide details, but the high-level summary is that the Android ecosystem is actually surprisingly safe. Given the size and complexity of modern mobile operating systems in general and Android in particular, I would expect the situation to be bad, but it's not.
With respect to Blackberry's work here, it actually sounds really good to me. They're doing a lot of good things, some of which we are also working on. I don't think any of the mobile OSes in current use are very resistant to targeted threats. What Blackberry is doing with this tablet is trying to tackle that problem: how do you secure high-value data which may be the specific target of a skilled attacker on a commodity, open platform device? It's a really tough problem. They're doing it by creating a locked-down sub-platform within the platform, allowing only whitelisted apps, preventing data leakage between those and apps in the open portion of the platform. That's a sensible approach. If they can really achieve protection against targeted attacks, the higher price point isn't unreasonable at all. People with high-value data on their devices will pay for security. Most people won't, but there's nothing wrong with focusing on a high-value niche. It's good business, and a strategy that's consistent with the reputation of the Blackberry brand.
Google, of course, isn't targeting the niche, but trying to provide reasonably good security to the mass market. My opinion is that we're largely succeeding, but must keep pushing hard to stay (mostly) ahead of the threats.
(Disclaimer: Please don't take this as any sort of official Google statement. I'm not a Google spokesperson, and I'm taking something of a risk by being this forthright about Android security work in public. Not a huge risk, because my management is supportive of transparency -- as long as I don't cross any lines. I obviously haven't gone and cleared all of this with PR and it's possible that something I've said is inaccurate, or inconsistent with the company's official position. If there are any such issues, the fault is entirely mine.)