She's a "pop star" in the UK. Technically she is both popular and very good but I find her music a bit...lacking in most places. However, saying that I find the lyrics to the song "The Fear" quite good.
Now for the why. She has recently joined a group of UK musicians who are trying to decide what kind of punishment should be given for people who download mp3's illegally. Even before this she has a reputation for being vocal about almost everything and so shes combined these two and a lot of people have lost interest in the integrity of this council now.
Hope this explains.