The short answer, the 16 Gbps is the total available aggregate bandwidth for an 8 gig (duplex) link Etherchannel, although on such an Etherchannel the best bandwidth a single flow might achieve from host A to host B would be gig.
When FE and duplex first came out, Cisco (sales?) liked to say individual links had 200 Mbps of bandwidth, this to make them seem twice as good as FE half duplex links.
Although, of course, with duplex there is 100 Mbps in each direction, for a single data transfer, from host A to host B, maximum throughput is still 100 Mbps. I.e. in theory, no faster than half duplex unless there's also host B to host A traffic too.
I.e. Cisco (sales?) seemed to preferred saying it was 200 Mbps rather than 100 Mbps full duplex. I suspect this may have been done because it sounded better.
Cisco, though, is occasionally inconsistent on how to describe duplex bandwidth (read up on the 6500 bus bandwidth, it's usually referenced as 32 Mbps, but occasionally it's referenced as 16 Mbps [I believe it's actaully 16 Mbps duplex]), but Cisco still most often doubles the bandwidth for duplex "infrastructure" links, such as when referring to Etherchannel, 3K stack ring or fabric bandwidths.
