Re: TDKR SPOILERS (read at your own risk) - Part 5
Pretty sure he faked his death so he could be with Selina. She wanted to "disappear and start fresh" and I think he did too.
Alfred clearly states that Gotham is a place of tragedy and haunting memories for him. If he stays there, then he'll slip back into being Batman.
He faked the Bruce Wayne death so that not only could he start fresh himself, with Selina but also so that everyone else in Gotham could. He could give his house to the orphans. He could let Alfred finally effin retire. Fox could run the company without issue. All of that. Again, as Alfred said, "There's nothing there for him."
All that said, I am slightly bummed he left his father's name in ruins. I would have wished that at some point Bruce Wayne would have done something so that people would have seen him in a different light before he "died."