Its great to see these design challenges, Fantastic effort from Threadless to work with causes like this.
So heres my contribution,
This design came to me while looking over the wearethorn website and reading what their goal is and seeing the words " disrupt predatory behavior" and also to make the internet a " hostile environment for those who seek to exploit children"
That got me thinking along the lines of predator and prey, and then seeing the use of a thorn in their logo which I thought looked kind of like a shark fin.
that led to the idea of Thorn pursuing these predators online, which led to the use of the www. as waves.
And finally I went with the Blue and white that you get when you highlight a link for the colour scheme.
Anyhow, just a little explanation of my thought process.