Are we going to have to whitelist every currency that will exist in the future? At least have a pay: schema so you do pay:bitcoin.com/... or something.
No. Evernote, dropbox and flickr are all services implemented by a single organization each. You could just to use HTTP to link to a flickr profile. Bitcoin is decentralized. It is like a protocol. Each user can have his wallet stored in a different service, or even in his computer.
The spec allows a wallet service or an application to add itself as a handler for bitcoin: links. Similar to mailto:, the user can choose the application which can listen to those links. It could be gmail, or thunderbird, or outlook.
Its like a protocol but if it was a protocol it could be used by different currencies. Just because it is distributed does not mean it cannot have a URI to identify some metadata about the currency being used.
My point is.. you can have any application or service to handle bitcoin address clicks. You can choose to open your wallet service on any website, or an application which manages your bitcoins stored in your hard disk. It isn't a HTTP link, and there isn't some central web service to transfer bitcoins.
Both paypal and googlecheckout are implemented in one way. It is not a protocol. Only the service's website can handle the request for payment in those currencies. Bitcoin is decentralized. The user can install/associate any service/application to send bitcoins, much like emails using mailto:
