There isn’t room for even 20 major online ad companies in the long-term, let alone the hundreds that exist today

Meanwhile, a host of online ad firms are chasing finite ad dollars. Witness the number of companies that provide “demand-side platforms,” for example, which are essentially software tools that automate the process of buying online adverting. There are dozens of companies on the list, including Media­Math Inc., Turn Inc., DataXu Inc., The Trade Desk Inc., AudienceScience Inc. and Merchenta, to name just a few.

via Burst of M&A in Online Advertising as Shakeout Begins – CMO Today – WSJ.