Facebook is apparently developing a new platform to deliver contextual ads based on its members’ preferences and interests.

The Wall Street Journal reports that the system is the social networking site’s “top priority”, although details are sketchy and it is in the early stages of development.

It’s also not clear how it fits in with Facebook’s current ad deal with Microsoft – on which the site relies for much of its revenue.

According to the WSJ, the solution will show ads in the news feed section of members’ pages, while brands will bid for keywords via an automated booking system, á la Google Adwords.

By scanning its estimated 40m member profiles, it will apparently expand upon Facebook’s existing targeting capabilities, which allow brands to tailor their ads to members’ age, sex and location.

The report says Facebook will be able to “predict what products and services users might be interested in even before they have specifically mentioned an area.”

The blogosphere doesn’t seem wholly convinced that it’s a majorly significant move, but it does seem inevitable that Facebook is going to make more use of the personal data its members reveal on their pages.

If the system was extended beyond text ads, it also seems likely to be welcomed by brands and agencies that are concerned about where their ads are appearing on Facebook, as well as other sites employing user generated content. In turn, Facebook would be able to raise its CPM fees, which TechCrunch reckons are about $10.

In the meantime, though, Facebook could be beaten to the punch by application developers that are already using its open platform to develop ad networks and build up information on its members.