<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by WHBM:
Yes, I know getting miles on another carrier is great, but all that could be done on the computer WITHOUT actually assigning multiple flight numbers.</font>
I don't think this is ever the motivation for codesharing, at least for US carriers. To give an example, NW and CO codeshare with each other quite a bit. But, FF members already earn full credit including status bonuses and elite qualification on either carrier's flight, so there's absolutely no benefit from a FF point of view.
I think that traditionally, codesharing is done by mainline carriers to "extent the reach" of a carrier, filling in holes in their route maps.
<font face="Verdana, Arial, Helvetica, sans-serif" size="2">3. Passengers have no idea who is actually operating a flight.</font>
This should never be the case, at least in the US. A law was passed a few years ago requiring that the carrier actually operating a codeshare flight be disclosed to the passenger before they buy a ticket. All of the online booking systems, whether they be run by an airline or a third party, now make this quite clear. I also think the airline phone agents disclose this. I would assume that travel agents are under the same requirements, but there are no doubt some that are sloppy and don't do it.
I think you have made some valid points though.