Those of you who publish AdSense ads on your websites will probably be aware that there's an option to block unauthorised websites from showing your AdSense units. We've exercised this option and, as a result, have become accustomed to a yellow bar appearing at the top of the AS panel warning us that our ads have appeared on sites we haven't authorised (usually things like Bing, and a couple with mysterious IP numbers we don't recognise).
However, when I went to check our AdSense this morning, I saw we had an additional red message bar, plus a big red button at the top right of the screen saying "1 Alerts" (sic). I had a look, and found it was yet another site displaying one of our ad units.
I checked out the URL (ib.adnxs.com), fully expecting it to be a scraper of some kind. Instead, it redirected me to AppNexus.com, which on the face of it seems to be setting itself up in competition with Google (with backing from eg Microsoft and Kodak, according to their Wikipedia entry).
This looks to me like AppNexus cheekily exploiting the way AdSense works to try and push their own product. Am I right, or is there a more prosaic explanation?