The drunk and the lamppost
A man walked out of a restaurant to see a drunk searching for his car keys under a lamppost. He joined him in his search and, after several minutes, asked him whether he was sure that he'd lost his keys under the lamp. "No," said the drunk, "I'm pretty sure I didn't lose my keys here, but the light is best here, so I don't want to search anywhere else."
Moral: don't choose a research area just because the 'light is better there.'