Rae Hoffman was complaining on Google+ that the AdSense ads do not load when you are using the iOS Google+ app and then visit a site that does have AdSense ads.
I believe the issue is only when you use the in-app browser found in the Google+.
For example, I loaded a story on this site in the Google+ browser and then opened the same story in the iOS Safari browser and iOS Chrome browser. The AdSense ads loaded fine in Safari and Chrome but not within the Google+ browser.
Here are screen shots:
I can reproduce this myself and others can as well.
The question is why would Google block AdSense ads when they make money from them? You have to assume they are using a Chrome build of some sorts for the Google+ browser. So this is just strange. I am sure they will fix this in the next build.
Forum discussion at Google+.