Each attendee would have a unique QR code for the whole festival, which would be used when they purchased tickets via web, app, phone, or in person.

They could have an identity card & lanyard sent to them in the post, they could collect it, or they could show it on their phone / tablet.

At each show, the code could be scanned by door staff to automatically verify the booking, display how many tickets there are, and if appropriate, the seat reservations.

Each venue would need to have a mobile phone / other device with a decent internet connection (WiFi / HSPA+ / HSDPA / EDGE) to be able to receive the data pushed to them as it changed, and to be able to scan the codes.

As well as being a much simpler and more eco way of ticketing, it would also facilitate the collection of powerful metrics and reduce the possibility of fraud.

Would be nice not having to faff about with tickets, especially not having to wait in a huge cue to get them printed off!

Yes, this would also cut down on the infrastructure that Venues and the Festival would need to process tickets, only thing required would be a mobile in each venue.

Why is this different from the barcode idea

Because this is a single global identity for a festival, not a code for a single transaction / event booking.

A few more edge cases I've thought of since reading the comments on the other ideas:

- If you are buying tickets for multiple people who don't arrive at the same time, you can transfer the tickets to their account, so that their festival ID can be scanned too.

- It is a nice way to return tickets and make them available to an automatic waiting list (rather than have a queue at the venue).

- It makes life harder for scalpers - they can't easily walk in 50 people without raising an eyebrow, and can't sell festival ID's in the street without proving what's on them.

Same objections as to the other scheme - you are relying on lots of new technology, which will be great when it works fine but given the festival atmosphere will have a very very high rate of failure.
http://ideas.edinburghfestivals.co.uk/submissions/4261-what-if-we-had-a-really-simple-paperless-ticket-scheme-staff-just-have-a-list-of-names-at-the-door-and-you-show-id-see-1st-comment
http://ideas.edinburghfestivals.co.uk/submissions/4215-what-if-you-get-a-barcode-and-every-time-you-buy-tickets-they-are-linked-to-ur-barcode-and-it-s-scanned-as-u-go-into-shows-instead-of-paper-tickets
@andy T And it wouldn't cut down on the infrastructure the venues have to provide, it would massively ramp it up. Places like the Underbelly that have 27 venues (or something daft), some of which are little more that cupboards would need much more tech - and good luck getting a good data signal in that poky warren.

The reason I suggested QR codes rather than RFID / NFC is because anyone with a smartphone and an app can scan the cards / tickets. There's no need for venues to purchase special scanners / servers etc if they don't want to. In two years' time NFC will presumably be sufficiently ubiquitous to make that a preferred alternative, given the appropriate proliferation of the technology amongst phones.

The idea of the barcode was to associate it to you as a person, not to the event you are attending. ie I would have a barcode that meant Karen I and my tickets would be registered to that barcode. I wouldn't have a different barcode for each show I had booked.
Parkrun manage to run this kind of system at minimal cost. Maybe sponsorship from a techonology firm to overcome the initial capital set up costs of hardware and software.