Any hints from past experience? Any best practices? Any research on the subject?
I redesigned a community college site's IA recently with task-based navigation for a student audience - it has been quite helpful since students were the greatest audience of the site by far. The other audience channels were left as they are (Business and Community, Employees, etc.) but with a huge percentage of visitors interested in specific tasks on the website, setting up the navigation so students could complete specific high-traffic tasks was very beneficial to that audience. I have written up a case study on my personal site so you may find some answers there.
A topic based navigation can be done, but is not preferred, if you are unaware of the audience - such as a public website where users don't have to login to see content. Audience-based navigation on public web sites would have to be generic in the form of "I'm a parent" or "I'm unemployed" or even "I'm retired", but still you'd have to put every audience type in there.
Especially this is valid in government sites:
However, where you know the user, as in a public web site where users are signed in or even better in an intranet, audience based navigation is preferred. You could base navigation on which cooperation sites the user participates in showing only "my projects" as one example. Another would be to display content, such as news, based on audience such as you organisational belonging.
Just keep in mind that audience based navigation is much harder to implement and maintain, but for the user you could make a big difference if you only display navigation elements valuable to "me" as a user based on my properties.
Reference: Organize Content Based on Audience Needs