According to the [Stack Exchange TOS][1] all Subscriber Content must be irrevocably licensed to Stack Exchange under the [Creative Commons Attribution Share Alike](http://creativecommons.org/licenses/by-sa/2.5/) license. This requires us as members to have the right to give them such a license.

If a copyright issue occurs, normally a DMCA takedown notice is sent by the rights holder to Stack Exchange and they presumably will remove your avatar. You are the one who originally pirated the image so you are personally responsible. Stack exchange is probably also responsible, but only so far as neglect goes (which is not that far if they act upon all requests from rights holders).


  [1]: http://stackexchange.com/legal