You can buy an "impersonal season", which costs 50% more than the
equivalent Adult rate season ticket, but, as its name suggests, allows
any number of people to use it (although only one of them may be using
it at any one time).

Any idea (apart from the additional profit they'd lose) why they don't relax
the rules on travelcards and let them be used by the bearer? I think TfL
have relaxed this on weeklies now, only one person can use the ticket at any
one time anyway and it seems unfair in this case they have to buy two
tickets to do the equivalent of 5 returns. I'm sure the potential abuse is
quite small, the logistics of two people ticket sharing to get more than 5
journeys a week would be difficult..

D