The March 9 edition of RTBlog ("Trolling For Transparency, Media's
Latest Buzzword") incorrectly referred to WPP’s GroupM as being an investor in AppNexus. WPP invested in AppNexus as part of an asset exchange that includes parts of 24/7 Real Media. The
column also incorrectly referred to AppNexus as previously being a part of GroupM. While some of Xaxis’ team grew out of 24/7 Real Media, AppNexus was never part of Xaxis. Xaxis is a client of
AppNexus. The column has been updated with the correct information.