Yes, why is posting about anything nice 'bragging'? And I really don't get this 'it is wrong to admit to having/doing anything nice in case someone who doesn't have or do said nice thing gets upset'. That's life and even the poorest in this country are relatively fortunate on a global scale.
When people used to send postcards from holiday, the meaning was 'we are all still alive, hotel is great/OK/a dump, look at this lovely view/fat bloke with a stick of rock, see you next week' and surely, to most people, FB is just a modern day version of this?
Those who see evil intentions for some reason, when you got a postcard from your Aunty Beryl's week in Benidorm, you didn't instantly think 'oh look at her, flaunting her spare cash and cellulite on a week's all inclusive sun, sea and sangria. Why isn't she enjoying her holiday instead of pissing about with postcards, and anyway, I know she hasn't shagged uncle Reg since 1975 so how dare she claim to be having a lovely time' while we have a week in the rain in Margate'.
Yes, some people post pointless drivel about their breakfast, some people are overly materialistic and some people post about their real or imagined misery that is inappropriate for a public audience, but I really think a lot of the haters are overthinking this just a little bit.