I don't understand complaints about the fact that free third-party apps provide functionality that some other system has built into it inextricably. Unless there's an actual architectural problem with having a third-party application do something, that's a superior approach, because it allows you to choose the functionality you want and choose best of breed options rather than being essentially forced to deal with an inferior built-in tool that can't be removed.

If you doubt, try taking a closer look at Firefox. It was the extension system that made Firefox awesome, once upon a time. It is the monolithic growth of Firefox that has been destroying it.

As someone else mentioned in a response to this, believing that only Android is vulnerable to malware is naive in the extreme. There are security issues with the way iOS and WP7 have been implemented that leave them wide open to malware of various sorts as well. In fact, in some respects they come with malware built in (no need to add a third-party app to meet your malware needs).