I found another one. This has been a rather frustrating week for me, working around quirks in Android, many of which are clearly bugs (like this one, or yesterday's post) and others where the jury is still out.
Today, it's a problem with NotificationManager. Specifically, NotificationManager.notify() silently swallows invalid notifications. In particular, if you create a notification without calling setSmallIcon(), the NotificationManager will simply not bother to add it to the notification panel. Like yesterday's problem, this is particularly difficult to debug because there are no errors or warnings anywhere.
What makes the whole thing more interesting, is that if your notification includes a sound or vibration, those actions will still happen, which leads you to believe that the weirdest thing ever is going on since nothing shows up after the noise. Of course, that's slightly less weird than having it do nothing at all, which leaves a developer with absolutely no idea how to debug or proceed.
I hope the Android team manages to find time to fix some of these issues.