My first iPhone was the 8GB original and I never filled it. Unless I was going on a trip, I didn’t keep movies on my phone and music syncing consisted of a few recent playlists. That left plenty of room for photos and apps. Because of this, when I purchased my new iPhone 4 I opted for the 16GB model. Higher res photos and HD video will take up more space, but doubling my current allotment for photos only gets me to 2GB, and each hour of compressed video only gobbles up 5GB. That leaves plenty of space for apps. Plus, now I have an iPad for watching movies on long trips.

Then I started thinking about Apple’s new iAds. According to reports, the new Apple-designed ads will feature inline movie clips, games and other interactive features. This will take up additional space on your iPhone. Ad Age’s preview of the new service states the ads are downloaded when you sync your iPhone. This is good for the user because you won’t have to wait for an ad to connect to the web when viewing, but it means the ads are stored locally. Couple this with new higher res apps to accommodate the iPhone 4’s new retina display and iApps seem destined to get much much bigger. Those 16GB iPhones might start feeling cramped soon.

Updated iPhone 4 apps are coming out now. iAds goes live July 1. Keep an eye on your GBs.