Is there an OS wide manner for opting out of display advertisements on Windows 8?

As it currently stands, there's no way to opt-out of the ads. The "Ads in Apps" framework is provided by Microsoft to App creators as a unified advertising system to make monetizing their programs easier (and probably so MS gets a cut as well).

Just because the apps may have been bundled with Windows, doesn't mean the app creators don't (also) want to get paid by advertisements. :)

The assumption is that the ads are paying for the service that the App is using to give you information, not for paying for the app itself (eg: Weather2Travel.com in your example needs to keep their servers up to make the app useful).

Looking into my crystal ball: Will someone eventually figure out how to block them? Probably. Will MS change the framework so that the blocks don't work anymore? Probably. Will this be an endless battle? Probably. ;)