Want to know a quick road to a bad app review from your users? Local notification spam. Frankly, we're sick of it. You spam us, we'll toss your app off our phones like *snap* that.
Just because local notifications don't require opt-in doesn't mean that developers should abuse them for marketing. Here's a rule of thumb: if your notification doesn't deliver information that your user specifically requested, don't send it.
This goes for push notifications as well. When users opt in, they're not opting in for spam. One of my fellow TUAW bloggers mentions, "Ambiance is probably one of the worst, even worse than Disney. Every few days it tells you that 10 new Ambiance Exclusive Sounds were just added to Ambiance! I don't care."
He adds, "Oh, and spell check your notifications. Some of them are just embarrassing."
This is not the user experience you should be aiming for.
When your spam arrives in the middle of dinner or at 3 in the morning, you fail to win hearts, reviews, and customers. "I don't care if I have 9 tokens, I don't want to start your game with my friends now or...ever." Goodbye app.
Listen, developers -- user experience draws customers, not pushy sales techniques.
And don't try to weasel your way out of this by saying "iOS 6 will solve this problem." Spam notifications are wrong, regardless of whether users can switch on "do not disturb." Rationalizing like that is a cop-out that doesn't address the fundamental issue.
Apple (at least theoretically) refuses applications that send ads through push notifications; you should follow that for user notifications as well. Stop the local notification spam and win the hearts, loyalty, and respect of your users.
Thanks to all the dev buddies in #iphonedev on irc.freenode.net who gave feedback for this post.