iPhone iAds: Very inconsistent, sometimes bannerViewDidLoadAd does not get called

So I show my iAd banners when I get a callback to: 'bannerViewDidLoadAd'

But I've noticed that sometimes this doesn't get called. I have a constant high-speed internet connection but if I run my app 10 times. 4 of o开发者_高级运维ut 10 times it won't show the iAds (i.e., bannerViewDidLoadAd does not get called).

Has anyone else experienced this (and what have you done about this)?

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This is by design (I'm assuming you're still running in a dev environment) so that you can test your application when an iAd is available and when an iAd isn't available.

While you are developing your application, iAd Network sends test advertisements to your application. To assist you in validating your implementation, the iAd Network occasionally returns errors to test your error handling code. You can also test your error handling support by turning your device’s wireless capability off.

per Apple's documentation