That's a nice commons you've got there. It'd be a tragedy if something happened to it.
As has been extensively discussed, there are lots of drawbacks to the App Store model. But if they actually enforced limits on push notifications (or maybe even charged developers for them), it'll slow the tragedy of the commons a bit. I agree that individual users could do the same, but the marginal spammy app still has every incentive to be spammy.
Charging developers is probably going to result in the opposite of what you want: notifying the user of something useful probably monetizes far less than the spammy notifications instead.
Apple just needs to get a grip and start swinging banhammers, like Facebook did with Zynga. Put troublesome apps in a probation period, where notification strings end up going through an approval process. And punish developers by holding subsequent apps up in the review process.
As has been extensively discussed, there are lots of drawbacks to the App Store model. But if they actually enforced limits on push notifications (or maybe even charged developers for them), it'll slow the tragedy of the commons a bit. I agree that individual users could do the same, but the marginal spammy app still has every incentive to be spammy.