I will be establishing a community WPmu site and want to be able to customize and target advertising according to user blog/content. They get the blog, I get the advertising rights.
Is there a suggestion of the best way to manage this. I am expecting that it be in the footer template, but I am looking for "how to" guidance.
Will there be anything about release 2.7 that would make this possible/easier?
Google adsense targets that way. There's quite a number of plugin out there to insert them all over the blogs.
"Will there be anything about release 2.7 that would make this possible/easier? "
nope.
If you want to take the easy way out, take a look at the admin bar plugins, add some height to it, and just stick the google adsense javascript into it.
Your percentages are going to royally suck but it's an easy way out.
