Cap:

Another continuity error in my opinion is when Ben says that Luke was hidden from Vader. This may have raised an eyebrow in ’83. (If they’re trying to hide him, why keep the same last name?) But when the PT came out, we learned that Uncle Owen was Anakin’s stepbrother, and apparently living in the same place that Anakin knew. With that information, the idea that Luke was placed there to hide him from Vader becomes particularly hard to believe.

Well, aren't you missing the fact that Vader didn't even know he had a son, and so wouldn't be looking for him? And why would Vader care what his "step-brother" was doing? He only met him once several years before and probably never cared to return to Tatooine again after the death of Shmi.

Bingowings:
Even the most fantastical tale has to follow it's own internal logic.

Man, how I wish everyone understood that.