iphone media package or iphone data package? someone wonder when buy an iphone 3G, does they buy iphone media package or iphone data package to use the apps for the internet, or if they use Wifi will it charge to bill as opposed to using the phone internet service ?

YES. Every single smart phone requires it (Blackberry, Palm, Motorola, etc.). in fact, everytime AT&T activates an iPhone 3G, they pay Apple $425 (so the iPhone 3G is actually more expensive than the original). So think of Apple selling the iPhone 3G to AT&T for $425 and AT&T is selling it to us for $199.

AT&T cut the price to draw more customers. To make up for the huge price difference, they’re making the iPhone 3G in-store activated (like all the smart phones), raise the data plan to $30 per month (instead of $20), and Apple is no longer taking a portion of the iPhone’s monthly bill from AT&T.

All that will actually end up making the iPhone 3G more expensive than the iPhone in the long run. If you didn’t have a media package, watching a single YouTube video (3 minutes about) is approximate $600!
There’s also no point to just using Wi-Fi. The cost of the iPhone isn’t worth it without being able to use the internet anywhere.