What the hell!?!? I love the earrings and the jacket, but come on, girl - wear a shirt once and a while!! A few days ago she was walking around in a white button-down, wide open, with her orange bra hanging out, trying to make it a 'look', and now this. This girl's got style - I don't know why she insists on making herself look like an off-duty stripper recently.
Pasties belong in burlesque shows and not part of fashion wardrobe to be worn on the streets. There is way too much focus on sex and fetish in fashion currently. And while there is always going to be a certain amount of sexiness in our clothing trends, there is a better way of going about it than that and a definite line. And in that photo the line is hanging about the knees or ankles...
If you're wearing nipple covers with the intention of showing them off then you're inviting accusations of crassness (while I think this is going to become more commonplace, I don't think society is ready for it just yet).
On the other hand if a girl is wearing a plunging neckline (which Rihanna is not) and can't wear a bra with it, then she needs to turn to a solution such as nipple covers should a slip up occur.