I added the ADBannerView to a view and when I load the app I get the following message:
ADBannerView: WARNING A banner view (0x7a023c0) has an ad but may be obscured. Th
I got the same problem but the reason is I have OpenFeint notification bars on top of that, e.g. high scores, achievement unlocked, etc. It slides in and then slides out, does not stay for long, so I don't think it is a problem.
I you put ADS on the top, then user would not see OpenFeint notifications, that will be another problem, I do not know if this happens if you have ADS and OpenFeint on different locations of screen, I did not try it as my app's bottom screen is full of buttons, so only top of screen is available.