Maybe in console shooters, but I've played lots of shooters on PC (Which is my preferred platform for games in that genre anyway.) that don't have it. It seems like this sort of mechanism is primarily done with console gamers in mind, and I can understand that, because it can be hard to pull off precise shots with a controller, which is precisely why I prefer to play first person shooters on PC, and it annoys me when conveniences like these designed for the console versions are forced on me in the PC version.
Thus, if this is in the game, I hope it's possible to turn it of, and there's no guarentee it will be, in Fallout 3, there was no option to disable auto aim, that's why there are mods that remove it, or reduce it as much as is feasible, since my understanding is that removing auto-aim entirely messes up shooting in Fallout 3. I can live with auto-aim in console games because, as I've said, aiming precisely can be difficult with a controller, but in PC games, I don't want it, especially if it's like in Fallout 3 where not only was it trying to help me in something I didn't want to be helped in, it could actually prevent players from using the strategy they intend to use because you might be trying to shoot a mine or car or other explosive object near to the enemy while your shots keep going towards your enemy. And I never had any trouble hitting in Oblivion either, except when I'd expect to have a bit of trouble hitting, like when trying to hit a moving target. I don't want this to be forced on me and if Bethesda must put it in to appease the console players, they should at least include the option to turn it off.
At low level you have a spread, holding a bow drawn will reduce accuracy, this is also depending on bow type as you would be far more inaccurate with a heavy draw bow than a light. At high skill levels your arrows helps hitting the target if you miss by a foot.
That has nothing to do with auto-aim, though, it can be implemented without it present. The idea of the auto-aim or target magnetism or whatever you want to call it is to make it so your shots will veer towards the target slightly even if you're aiming a little off, or the crosshair will "follow" the target to a degree or automatically "lock on" to it in aiming, I've seen both implementations. but what you're suggesting would be independant from the target's actual location. There would just be a degree of "spread" to your shots so rather than always hitting exactly where the crosshair is pointing like in Oblivion, they'd hit within a certain area around it, so they might go off from where you actually want to aim at, and most modern first person shooters have this to a degree, whether they have auto-aim or not, just that, for the obvious reason of character skills not being present, it isn't based on character skill, it's just based on the accuracy of your weapon, whether you're crouching, whether you're moving, and such. And this is more or less realistic because in real life, you won't always necessarily hit the exact point you're aiming for, auto-aim, on the other hand, is not realistic unless you have some sort of science-fiction gun that automatically adjusts you're aim because in real life, you're shots won't automatically adjust to where you want to shoot.
Although I DO hope to see something like that in Skyrim anyway, as far as I see it, it's the best way to handle ranged weapon accuracy in a first person RPG.