Before I start I just want to say that I think it should be but, I'm not evangellical about it. If you choose not to, that's fine, as long as you don't stop others who want to. I work in retail, on mat leave atm, and have often had to serve (silently) customers who ignored it.
So....
I sat down to try to snatch a cuppa and a bacon sarnie in Tesco cafe this morning. DD was due a sleep so I was hoping she wouldn't kick off as it was almost 11am.
There was a tannoy (not easy to hear over the noise of the shop but given the time it seemed obvious to me that it was) informing everyone that the 2 minute silence would take place shortly. Some staff appeared from behind the scenes and stood in the cafe.
As the place quietened, I was aware of a woman sitting at the next table talking softly. I presumed she hadn't heard the announcement or was not observing it for her own reasons. She was asking her husband why the till staff weren't standing when the cafe staff were, and how it was so disrespectful of the event. 
I was wondering if I was braver what I would've said. But I can't think what I would've said. I still can't work out her out and I've been thinking about it all day.
Btw, I know some of you will say MYOB but I'm seriously interested in trying to understand her logic.