I'm going to offer you an option, a description of how things work at my house, for you to consider. I have two boys.
Each child gets a cell phone and a laptop when he goes to college. On the other hand, he gets a simple mp3 player that does not connect to the internet, as soon as he can be trusted not to lose it. The desktop computer is in the living room. The child doesn't have an account on either parent's laptop. The child's desktop account has strict controls, which get gradually relaxed as the child matures. Age 11 at our house generally needs maximum controls. I do not allow google and I especially do not allow google images at that age.
On the other hand, if the child wants to buy himself a magazine with curvy ladies from the drug store... I can live with that.
I think some of the porn-seeking behavior is a bit like a moth seeking the flame.
Also, I think an over-exposure to pornography can get both young men and young women confused about what they think one is supposed to enjoy, versus what they and their partner do enjoy. And it takes away some of the miracle of discovery with the partner.
If you don't have a good book written for boys about sexuality on hand, it would be a good idea to pick one up. The one I chose last year for my then 11yo is called "It's Perfectly Normal." You have to go to the bookstore and browse, so you can choose something that feels right for you and your son, though.
You can go to the movies together, as a family; the movies you choose can get very gradually a little more risqué. You want him to have mental images of healthy, realistic romantic interactions. I don't mean people having sex -- I mean people developing relationships, feeling attraction, figuring out how to act on those interests, getting through difficulties, etc., and you want the child to see some images of kissing, hugging and caressing in this context.
Let's not throw the baby out with the bathwater. Can you give him back some computer access, but with safety built in? On our Windows 7 desktop, we have had good results with Windows Live Family Safety, which is free. I can choose the settings my child needs.
A couple of times a week, I sit down at the desktop with my son, and we go on my account (no controls!) and we surf TOGETHER. I have absolute veto power.
Try to find some adjustments that will convey the message to your son that what happened was understandable and normal (but not healthy), and that you don't blame him. So that he doesn't feel guilty about what happened. You might want to discreetly point out the curvy ladies magazine section next time you're in the drug store.
I hope some of our customs give you some ideas for things that will work for you and your son.