Yarn bombing is a type of graffiti or street art done with yarn, either crochet or knit. So the question asked; is it art or vandalism? Technically it is illegal as with any other graffiti. However, it is rarely enforced.
There are many places one can find this art. Most of the time it is seen in cities…
Park benches:
Trees: 
PIPES
I recently watched a video of a yarn bomber, London Kaye. She was interviewed on CBS news https://www.cbsnews.com/videos/how-one-yarn-bomber-is-redefining-street-art/
WOW!!!
Here is a simple project I might try…
It would be a fun way to use up bit of yarn. Kind of like free form crochet!
So I would love to hear what you think. It is art or just another form of vandalism?
Happy Creating! Anita