It depends on the loads really. Some routes are really overbooked because they have a high no-show level. They will upgrade by picking an airline`s own loyalty card customers first. If you go to somewhere like LA in the late summer months, there is a lot less business traffic but lots more holiday traffic. They will way overbook `down the back` knowing that they will put quite a lot of those passengers in Business. SFU won`t really be put by anyone`s name - it will just be done. You could get SFU put by your name if you have a word at check in (particularly if you`re on honeymoon or something). Apparently in the States, they overbook quite freely but it`s not really done these days unless it`s or operational reasons (ie overbooking)