To say that Facebook has to tread lightly around privacy issues is an understatement, especially with a targeted ad push underway. Rather than navigate that minefield once more, the social network hopes to skip it entirely by posting an overview of how the ad system tracks habits while retaining our anonymity. For the most part, Facebook walks the fine line carefully. Its Facebook Exchange auction system relies on a unique, untraceable browser ID to target ads to specific people without ever getting their identity; both a mechanism targeting ads beyond Facebook and a Datalogix deal to track the ad conversion rate use anonymous e-mail address hashes that keep advertisers happy without making the addresses readable to prying eyes. The initiative sounds like it's on the right course, although there's caveats at work. Opting out of any Facebook Exchange ads requires tracking down individual ad providers, which isn't likely to result in many of us leaving the ad revenue stream. Likewise, those who'd object even to the completely anonymous ad profiling don't have a say in the matter. With those concerns in mind, it's doubtful there will be many significant objections in the future -- Facebook knows its advertising money train can only keep churning if its members are comfortable enough to come along for the ride.