Keep in mind that at the moment the whole process is anonymous. The photographs aren't taken in strict ticket number order, no names or anything are taken and you couldn't just use the details from online orders as some people buy on the day. So currently there's no way of knowing who is in each picture or what ticket number it relates to.
The iTunes analogy isn't really valid as everyone is buying the same thing. In this case you'd need to ensure people only got the picture they were in and not any other, and couldn't buy any other.
If there was more time I guess you could take people's details in the order they go through but you do realise how quickly this happens? It's literally step in, picture, step out, next. There was 3 photo areas all running together at the last LFCC and people were sometimes running from one to the other when they're shoot times clashed. Waiting for people to stop and give email addresses, make sure they've been taken down correctly etc will just lead to delays and hold-ups.
Not saying it's not possible as clearly it's done elsewhere but will probably require a big redesign of the current process. I actually like getting the print at the show which I scan at home and would probably only get the digital versions if included in the price. I spend enough already on all this stuff. If you had say 20 photoshoots (and some people do) and the digital copy was an extra £5, that's another £100 on top of whatever else you're spending. Money better spent on autographs or photos.
The obvious way of doing it to me would seem to be to use the image number printed on the back of each print and use that to log in and identify the pic you want after the event when they've all been uploaded somewhere but how do you ensure the right person gets the right pic and hasn't just guessed numbers for other people? Yes, I don't know why people would do that but if you saw some of things I deal with each day at work it's not beyond the realms of possibility.
These kind of privacy issues have already been discussed in other threads in the past. Just something to consider.
It would be nice if it was an option but as things stand it's not though I'm sure it's something that is on the organisers minds.
If people don't collect at the show then they leave a description and people have to match the description to the pictures left over after the show. Some people take passport type photos to attach to their slips which I'm sure helps but that's rare.
All manual and I'm glad I'm not having to do it given how many are sometimes not collected.
Thought they were just thinking about looking into it and may have a solution. We'll see soon enough if it's the event I think you're talking about.