As I’ve said before, my biggest quibble with the Star Wars prequels is the way ridiculous plot elements had to be shoehorned in to link them to the later stories, which didn’t work all that well anyway. This is the reason why children being introduced to Star Wars should see the movies in the order they were made instead of the order they are numbered (or Machete order).
If you watch episode four right after episode three, you realize that Obi-Wan moved to Tattooine specifically to keep an eye on Luke (because of course Vader would never look for him there), but instead spent twenty years in a cave with barely any contact with the boy. He also apparently spent much of that time forgetting details of his past, when he could have been preparing for how he would eventually handle Luke. This comic from Ryan Lutz at Terribly Drawn Comics illustrates those concerns in a nutshell. -via Geeks Are Sexy