First: Apps can definitely be mission-critical. If you're lost somewhere dangerous, your GPS and mapping app can be as mission-critical as it gets. Your app which makes a phone call (and, yes, I'm calling the be-a-phone functionality of a cell phone an app here) can be mission-critical.

Is that software held to the standards of mission-critical software? Probably not.

Second: There's a lot of space between the software which is recognized as being mission-critical and software which is just Bioware's latest patch target, and that software includes things like web browsers and the web server software which hosts your company's website. Given how essential a web presence is to, you know, being able to make money, web server software is hardly disposable, but it is not held to the rigorous standards of mission-critical software.