Given that the use of RIP as an abbreviation when someone dies is so widely used and accepted I'm sure I'll be told that I am being very unreasonable but I strongly dislike it!!
I realise when someone uses it they do so with respectful intentions but surely when someone has died it's not really all that huge an amount of extra trouble to type 'rest in peace' (or I suppose the original Latin, 'requiescat in pace')?
Whenever I see it I just think it sounds so lazy, unimaginative, and insincere in the face of something as profound as death. If you are going to make a genuine gesture of respect then why do it with as little effort as possible? 
It's not as though people are painstakingly engraving a tombstone, just typing for seconds on a keyboard.
I don't get it!