The things you find poking around in someone else's code…
The above screen was unearthed by a creative hacker crawling through the bowels of iPhoto '09, and strongly suggests the iPhone can — and may be — using some kind of hitherto unknown "Location" function to associate GPS log data with the photos it takes.
At its most benign, this could be used for pulling geotagging information off photos taken with another camera, or viewing a map of your travels pinned with the locales where you grabbed a snapshot or three.
Right now, this is just all blue-skying: if this "Location" app exists, it'd have to be running as a full-time background app (most current GPS apps are foreground-only), and the battery drain alone stands to be horrendous. If Apple in fact plans to role this out as an advertised feature, the privacy issues by themselves would have to be scrupulously ironed out ahead of time.