How do large advertiser distribution networks come about?

[NMC777]

This advertising agency (IMM) claims they have a huge advertising network that their clients can then use to reach millions of active Internet users. IMM Interactive - Beyond Performance Marketing

How could a competing agency, leverage what's already in existence to build something on a smaller scale, but to have something nonetheless viable and by doing so, compete with this? Thanks.

 

[bizzykehl]

I don't know about them specifically but I know a lot of these networks own their own sites, or atleast start out with that, and then add secondary markets such as right media to 'pad' their numbers, or just straight broker other networks (adbuyer).

took a look at their media kit, looks like that's copeac...hurrdurr me.