Dive summary: 

• Twitter announced last week that it will be launching an ad exchange that will allow advertisers to retarget users with promoted tweets; publishers shared their excitement with Digiday. [see full list at Digiday]
• The ads will use data collected by Twitter from the millions of Twitter buttons sprinkled across the web; publishers will likely be able to utilize their own proprietary data as well. 
• Barry Lowenthal, president of The Media Kitchen, said "Good for them. We love retargeting. It works for advertisers and it’s a great way to give users more relevant messages."

From the article: 

"James Kiernan, managing director, ZenithOptimedia
I think it’s a smart move by Twitter to enhance their capabilities and be in a position to capitalize on the growing trend of programmatic buying. By making moves like investing in an exchange, opening up their API, and offering self serve options will enable Twitter to further scale their business and help advertisers apply data in real-time to inform both their buying and targeting decisions."