Just what has Pippa Middleton done to deserve the tidal wave of vitriol that washes towards her every time she is unwittingly papped in the street.
No sooner had new pictures appeared in the papers at the weekend of the Duchess of Cambridge's younger sister and boyfriend Nico Jackson in their tennis whites kissing goodbye than the trolls crept out from under their bridges and logged on to their hate forums.
"Boring, disgusting, get a room, Mummy Middleton won't like that!, tacky ..." You get the drift.
Pippa didn't ask to be famous. She didn't ask the world to letch and paw at her backside, to see her as little more than a walking bottom, to turn her sister's wedding into some sort of perv-fest, freeze-framing endless shots of her buttocks.
And since then everything she has done has been viewed through the prism of a) whether or not you can get a good look at her bum and b) if it's suitable behaviour for the sister of a future queen.
Her harmless little recipe book Celebrate? Savaged. The myth being that she only got it because of her bum and her sister. Actually, the bookshelves are creaking with cookery books by foxy women – Nigella, Rachel, Sophie anyone? – with 'connections'.
Running sporting challenges for charity? Er, what was the bum wearing and what time did the bum do it in?
Her boyfriends? Up to Nico, she was a fortune-hunter out to make a good catch. Now that she's stepping out with the son of people who live in a £250,000 house and run a sports shop, she's letting the side down. Ok, he's a banker, but it doesn't quite cut the mustard. She can't win!
As it happens, both Pippa and her brother James show a rather sweet lack of social climbing in affairs of the heart.
While Nico is from an ordinary background, James's squeeze, Donna Air, is a single mum born into a working class estate in Newcastle-upon-Tyne. For all the accusations of Kate having set a 10-year trap to snare a future king, the Middletons actually seem much more relaxed about such matters than many of the obnoxious snobs who look down upon them.
For all the cachet, being Kate's sister clearly isn't endless fun.
In fact, most days now it probably seems to be a bum rap.