This is a chilling development. It means that your computer (and thus money and privacy) could be compromised by ads on a web site you visit.
Bruce Schneier reports in his security blog WWW Malware Hides in Images:
For the past two months, a new exploit kit has been serving malicious code hidden in the pixels of banner ads via a malvertising campaign that has been active on several high profile websites.
What a shame that the genius (evil genius) of malware developers is not put to work in positive ways. I also wonder how long Google’s ad revenues might last in the context of such exploits. It is a very strong argument for ad blockers.