E! - Kristin's Blog - Exclusive! Veronica Canceled -
http://www.eonline.com/gossip/kristin/blog/index.jsp?uuid=6bcc5753-bc66-41f4-8283-131667132231
"With actual tears in my eyes, I must tell you that I’ve heard from several solid sources that the CW has decided not to bring Veronica Mars back for a fourth season."