I suppose it would depend on the actual official reasoning behind
having photocards for period Travelcards in the past. Obviously there
is the issue about someone lending their TC to someone else to use,

They are so rarely checked in any case. I think only once last year was I
asked for the photocard, I was so surprised I almost became deaf to the
sound of the connecting door slamming as those wth no tickets escaped his
attention. Still, he was sure everyone who produced a season ticket had a
valid photocard, that's the main thing...

You still need a photocard for National Rail, but I see TfL are now
producing a combined Oyster/photocard with a picture and name on the front
of it, looks very much like an ID card to me -
http://www.atoc.org/traveltrade/news...8_25_12_04.pdf - most odd
though, since elsewhere in that newsletter it mentions photocards with
Oyster are no longer needed?!

Regards,
Dave