Popular ad exchange company adbrite has been shut down from feb 1 2013. Here is Adbrite Message on it closure :
Dear adBrite Advertiser,
Over the last few weeks, adBrite and its management have been evaluating the go-forward plan for the business. Given market conditions and certain financial liabilities, in working with our lenders, we have decided to cease operations on Feb 1, 2013.
This is a difficult decision for all of us at adBrite. However, after much deliberation this seems to be the best course of action despite the impact it will have on all the employees, clients and partners who helped build this business. There will be a team in place as needed to assist with winding down your campaign, and final reporting and invoicing.
Thank you for being part of the adBrite community.
The adBrite Team