Totally different purpose. "Fiber on mag-safe power port" can eliminate (doesn't have to) the Ethernet port and adds _any_ future ports that can be multiplexed into fiber's bandwidth. PoE on the other hand can't eliminate the power port due to:
1. PoE devices are not common.
2. Ethernet port will never be as ubiquitous as the power socket.
3. PoE 2009 is rated 51W max, macbook adapters are rated 60-80W (45W for Air).
4. Say future PoE comes out with 110W rating, Apple can't and won't trust all vendors to follow the standard to eliminate something as important as the power source.
If the PoE does not eliminate the power port, it adds nothing to existing macbooks.
1. PoE devices are not common.
2. Ethernet port will never be as ubiquitous as the power socket.
3. PoE 2009 is rated 51W max, macbook adapters are rated 60-80W (45W for Air).
4. Say future PoE comes out with 110W rating, Apple can't and won't trust all vendors to follow the standard to eliminate something as important as the power source.
If the PoE does not eliminate the power port, it adds nothing to existing macbooks.