Well this was a new one for me. As we were taxiing before take off this weekend the CC came to the chap next to me and to us both suggested firmly and politely that we put on our shoes on for take off and landing. This was not an issue of floor clutter in CW as mine were in the overhead locker. He was concerned that should we have to evacuate, then having no shoes would be sub-optimal. He did say that walking around in stocking feet in "broken glass and burning jet fuel" (his words) would not be good. I asked the CSD when he came round on the GC check if this was a new policy. He said that the CC was just being a bit over-enthusiastic as there was no mention of such a policy in "the book".
I remember reading here on FT some time ago someone saying that they always kept their shoes on as described; I thought it was a very good idea and I followed the advice for some time.