Well, 10 Megabit's per seccond isn't the same thing as 10 Megabytes per seccond. That's usually where people get more of the misunderstanding. A byte has 8 bits, so you're only going to see 1.25 megabytes per seccond on a 10bT link at the most. Then, you've got to deal with the overhead of protocols. Ethernet packets/frames are about 1500 bytes and have a small header(basicaly the MAC address of the sender and recipient). IP packets can be up to 64k and have a relativly larger header that has the addresses of the sender and the recipient, time to live fields, a checksum on the header, and other things I can't remember. It's a twisted web, but it all works out in the end.

Matthew
PS: All my numbers are from memory, so I could be grossly misrepresenting something...