Having used an iPhone, an Android phone and a Windows phone for more than a year, it always amazes me that there is no simple close button in any of the mobile apps. In iPhone you have to hit home button twice to get apps running in background, from where you can close those apps. Actually, I even didn’t know about this for a month. I was under the impression that as soon as I press home button, the app shuts down in a while. Home button in iPhone is already overused. So, chances are that after one or two years, it won’t react as fast as you expected to.
At least in iPhone, you can stop apps from using mobile data(3g, 4g).In Android it is even worse. You have to press series of back buttons to exit or you can use some task killer to kill the background apps. Also, what sucks is there is no way to limit mobile data app by app as in iPhone. Some apps come with a background service and it will keep running no matter what. So, your best bet is to kill all tasks frequently.
Windows (7.5) is even worse than Android when it comes to closing the apps. There is no easy way to kill task in Windows phone other than hitting back button number of times. Windows puts maximum of 5 apps in background, which you can see by pressing and holding back button. So, when sixth app starts, it will knock out oldest app from memory. But problem is if you reopen an app running in background by clicking it’s tile in home page or side menu again, the app will launch from beginning. Which sucks. However, it does not happen with in built Internet Explorer.The good thing about Windows phone is you can turn off background services installed by apps if you want to.
I agree that having a dedicated close button inside the limited screen space of a mobile may be too much. But, you cannot let those apps keep running in background after you switch to home page or other app. Simply because it will eat your processor capacity and your mobile data. Hopefully, someone will come up with an idea of dedicated capacitive button or some other trick to shut down a running app in near future.