Celeb Peek-a-Boo Bras: Totally Appropriate or so Not?

Open your eyes — sheer is all around us. And with sheer comes the inevitable showing of underthings. Some celebs, like Lady Gaga, go all-out, often revealing their entire bra. Others, like Rihanna, take a less in-your-face approach by giving a mini neon peek. Gwen Stefani, Margherita Missoni, Zoe Saldana, and Leighton Meester have also jumped on the bra-revealing bandwagon. Click through to see them and vote: totally appropriate or so not?