The problem is that bitcoin is not really mobile friendly - you need to wait an hour on average to have the transaction confirmed - this is OK for online stores but is useless for mobile payments.
Re-read, with particular attention to "directly hooks into an exchange".
If you don't have an account at an exchange but you don't want to wait for your beer, open an account at an exchange before heading out to the pub (or while waiting for confirms on your first beer order). Any exchange that fails to join the exchange-to-exchange SWIFT - uh I mean fast - private network so their customers can get quick service at retailers using any exchange on that private network might just not be the favourite exchange, at least for retail purchasing applications, of most retail-shopper types.
Yeah - but then you lose all the decentralization benefits that are the raison d'etre of bitcoin. Maybe this is the way to go - some compromise, a bit more complexity but much more robust and universal system. This could work especially well if married to the e-cash system
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