The extension of Yahoo!'s content network, combined with Ask's new direct pay-per-click service (and the ramping of pay-per-call) reflects the emergence of multiple online advertising silos. (Let's not forget MSN.)
The whole online advertising proposition is becoming more complex, even as it becomes more important. SEM firms that stand between large and small marketers and the increasing complexity of all these networks will correspondingly be more important going forward.
Speaking of pay per call . . . one of the provocative datapoints that The Kelsey Group pulled from its most recent SME advertiser research (Wave VIII of the Local Commerce Monitor) indicates that by an overwhelming majority small business advertisers (71%) would rather pay for calls than clicks. I'd share more, but people I work with wouldn't want me to do that.
More of this data will be presented at The Kelsey Group's upcoming Directories/Yellow Pages conference in September.
Related: Yahoo! Publisher Network