Jeff Jarvis is calling for an "open source ad tag," something that would allow potential advertisers, no matter what service they used to place advertising online, to have a way to go to one provider and buy ad space on big sites, small sites, your blog, my blog, and whatever else might fall in between.  Some of the commenters have already brought up the one concern that comes up - good faith.  When anything is "open sourced" like this, there is the potential for abuse.  If there isn't a way for the 'moderation' of this system to be easy for publishers to use, it won't be adopted, simple as pie. 

While the idea is fantastic, the existing ad networks would have a big problem adopting something new, since they surely like their market share - hence the fact that the "something new" might have to take this open source issue to task.  Then, the issue becomes getting publishers to shift from whatever they are using - or pressure their own ad providers to do so.  Let's not even begin to fathom the chicken/egg-ness of this whole discussion, though.  It's a great idea.  Now where do we all sit down to figure it out?