Apple filed a patent application for a method to get and add metadata to files automatically using social networks. Because who wants to sit around entering it manually?
Aperture (#4): Apple addresses IPTC/ metadata issues
Aperture Special Report: IPTC/ metadata issues
Aperture Special Report: Solution for importing metadata from iView MediaPro
Image Capture to iMovie import bug: Missing metadata the cause?
Aperture (#8) 1.0.1: keeps appearing in Software Update after it is applied; metadata issues not fixed; more
Aperture (#3): Another method for doing RAW conversion in ACR; Problems importing metadata; Crash culprits; more
Aperture 1.5 released: Library now allows images to be stored anywhere, new metadata tools