On April 8, Apple revealed version 4.0 of the iPhone’s operating system, marking their latest major upgrade to the revolutionary device that redefined the smart-phone competitive landscape.

An iPhone app displaying an HTC banner ad using the traditional ad delivery model we see on all current smart phones.

The new upgrade brings a number of features (over 100) that iPhone and iPad users and application developers have been yearning for. New features include multitasking, having a choice between individual email inboxes or a unified inbox, and the ability to organize your home screen apps into folders. OS 4 will be available to users in the summer of 2010.

For users of VoIP apps like Skype, new multitasking will allow VoIP apps to work in the background while you use your iPhone for other things, and even when your phone is off! This means that your VoIP call will ring through like a regular telephone call.

For Skype users who make international calls using free calling over WIFI (like me!), this feature finally provides true phone cloning and removes the issue of not being able to make or receive on-demand calls to/from your Skype contacts because their application is not turned on.

To people in the online/mobile ad business, a more exciting and trend-setting feature is Apple’s new mobile advertising platform: iAd. Below is Apple’s description of the iAd platform:

iAd, Apple’s new mobile advertising platform, combines the emotion of TV ads with the interactivity of web ads. Today, when users click on mobile ads they are almost always taken out of their app to a web browser, which loads the advertiser’s webpage. Users must then navigate back to their app, and it is often difficult or impossible to return to exactly where they left. iAd solves this problem by displaying full-screen video and interactive ad content without ever leaving the app, and letting users return to their app anytime they choose. iPhone OS 4 lets developers easily embed iAd opportunities within their apps, and the ads are dynamically and wirelessly delivered to the device. Apple will sell and serve the ads, and developers will receive an industry-standard 60 percent of iAd revenue.

With iAd, Apple once again proves their dominance in the area of providing game-changing innovations to the market place. This new way of delivering ads within mobile applications is poised to improve click-through rates for advertisers, and will become the new standard that other mobile platforms (Blackberry, Android, Symbian, etc.) have to measure up against when delivering ad content through their applications. No longer will it be acceptable to kick the user out of the app they’re using whenever they click on an ad!

The iAd also provides Apple with a new revenue stream, marking the company’s entry into ad serving. Together with iTunes and the new iBooks store, iAd is yet another bold step in Apple’s strategy of vertical integration.

Additional information on the OS 4 can be found in Apple’s press release. In the video below, Steve Jobs demonstrates some of the features mentioned of the new operating system.