I also thought the same thing after watching Inception but the movie raises more questions than answers about the possibility of entering ones dreams, I don't know how much consultation the producers did with actual scientists/doctors etc. Didn't Jenifer Lopez also do something similar in The Cell?
Believe me, when you pass out in my pad and I squat on your face with my hairy balls and asshole, THAT is going to be entering into your subconscious and dreams.
Inception is bloody difficult as it's hard to plant an idea in someone's mind, the subject's mind can always trace the genesis of the idea. True inspiration is impossible to fake. But extracting valuable information from a person's subconscious could be possible someday