I'm not really a fan, although they are harmless enough.
I knit, and get so fed up with people (ie non-knitters) suggesting that I make things like this, as though I had nothing better to do. I'm also a bit uneasy about people taking it upon themselves to decide what public places should look like - a bit like graffiti artists, but at least the yarn things are temporary. I realise that that sounds grumpy though ?.
I did see a lovely one made for Armistice Day. It was in the shape of a WW1 soldier - his head with hat on and the shoulders of his uniform.