I think you need to get some perspective on what it actually means.
It does not mean that the iPhone OS itself will display ads.
It does not mean that apps you buy will have ads.
It just means that there is a common Apple-supported platform for developers to add ads, if they should choose to do so.
Developers are going to do it anyway. Just consider it now sort of like a documented API, instead of using an unsupported/undocumented API. And if there are ads in paid apps, then the developer will take a caning from their users and people will stop purchasing it, and review it down. It will become common knowledge, the market will decide, and the app will fail. Exercise your consumer power to patronize vendors who do not put ads into their paid apps.
Now, having said that, that doesn't mean I still don't like ads in apps. I don't like ads anywhere.