I've read several posts where people say that its an error not to call "inside" during a race. In my book, calling inside means "get out of my way so I can pass you on the inside of a corner." It does not exist as far as I'm concerned.
Rule no. 1 of bike racing is that they cyclist in front has the right of way, period. The cyclist in front has the right of way not because its moral, or agreed to after long deliberations in the world court of cycling, but because if two cyclists cross wheels, the cyclist in back always loses. If someone wants the inside, then they have to take it by at least getting right next to me. At that point, no one has the right of way because wheels aren't crossed.
When I hear inside called in a group ride, I chuckle to myself. I give then room if I can, but out of courtesy, not because they are entitled to it.
If someone tried calling "inside" during the last corner before the final sprint of a race, I would close the door on them and pin them to the curb.
Now, if you are off the pace and a faster rider or group wants to pass you on the inside, thats another story. If you are off the pace you should go around a corner leaving room both on the inside and the outside and letting faster riders by. But if you are keeping up in the pack, "inside" does not exist.