It's Not Anarchy, It's Awful (NaMoBloPo #28)
I have just begun another Coursera course. The last was on Gamification, run by the University of Pennsylvania, and was brilliant. This one is called "How to Reason & Argue", run by Duke University, and I've already learnt a lot. For instance, explaining and persuading are ways of arguing. When explaining, the conclusion is already agreed to be true and it is the premise that is being discussed. When persuading, the conclusion has not been agreed and the arguer wishes to bring the arguee to agree with their conclusion. Not knowing the readers' feelings on the topic I don't know if I am explaining or persuading but my conclusion is...
Guerrilla knitting and yarn bombing are a waste of resources motivated at best by a wish to bring craft to the attention of a wider audience and at worst by a self-satisfying desire for attention.
Knitting is awesome. And crochet is ok too. Weaving, spinning all good. Felting - if you must. Some people think it is all grannyish. Some can't see the point. Fair enough. Such people probably have interests I would have similarly unenthusiastic opinions about.

The thing with knitting though, is that it makes something actually real and usable. Graffiti changes an existing object from one colour to another. There's not much else you can do with paint other than paint something. But knitting can be used to clothe something - usually a person. It can be used for comfort or warmth. It can give someone a way to keep warm or give a bit of comfort to someone who has nothing else. Knitted toys comfort children who have been orphaned in war zones, "angel blankets" give parents of still born or too premature children something to hold their baby in before they say goodbye. If you've got time and the yarn to think "oh yeah, I could use this to make a tree cozy" then you could change that to "oh yeah, there are charities needing knitted items so I'll knit them something."

To waste your time and resources making some self-serving piece of neon craft vomit which will become bedraggled and hopefully be cut off within a few days is just stupid.
Be smart - create with a real purpose, not with pomposity.
Charities in the UK Looking for Knitted Items
Loving Hands All sorts of items needed for lots of projects
Upon Butterfly Wings Angel Blankets
Knit-A-Square Knit an 8" square for AIDS orphans
There are lots more! Look at charities in your local area and ask what they need.