From the vehemence displayed above, it's obvious I'm playing to the unreceptive. Nonetheless, I shall undauntedly and cheerfully attempt to spread enlightenment amoung the masses

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Vermillion: I'm equally at home with or without a padlock feature in a sim. But you're only half right when you say only experienced pilots can follow a target with their eyes. Detecting the target in the first place is the truly hard part (read any number of accounts by WWII pilots; they say the same thing). Once you've spotted it -- assuming your line of sight isn't blocked or you don't look away for too long -- even an inexperienced pilot can rubber-neck around to watch it. That's not what SA is about. SA, as described in Shaw's and other text on aircombat, is generally described as the ability to know at any instant in time the total air picture around you. In it's most perfect form, it's knowing not only the location of every threat near you, but also their attitude, general heading, and energy state, as well as your own A/C's like parameters, and those of any friendlies too. And, it's being able to maintain that awareness while operating a complex piece of machinery.
The padlock implementation that's been suggested here would absolutely HAVE to cause a loss of "lock" if any aircraft, atmospheric, or terrain feature obstructed direct line of site. No argument there. Additionally, I've suggested that looking away from the pad-lock view for more than a few seconds would also cause a loss of lock. The pilot would then have to manually switch views until he re-acquired the target, and push a button to re-lock it. In one sim I've played, hitting the "T" key would cause the lock to flip sequentially through any targets in the currently sellected view.
Don't think for a second that an implementation like this would be a crutch for dweebs. In fact, it makes the possibility of target fixation (as mentioned gleefully

by Westy, above) all the more likely, particularly amoung inexperienced pilots. More than once while flying F3.0 I flew into the ground or had my emphanage shot off because I foolishly remained padlocked on a target for too long. I'm not asking anyone to admit they're wrong, just admit the possibility I might be right

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Rojo (a.k.a. Sabre)