Author: H.User1325 (9 May 13 6:01am)
If I read correctly, you can use your one key for all websites.
I read "Each user of http:BL must also request an Access Key to make use of the service." You are a "user" that has several websites.
If you try to get a second key, you're told you already have one. You would have to have another account to get another key.
I would think that if you are the admin for all websites; then one key ~~ You control the use. On the other hand, as a designer if you build the site and turn it over to someone else to run/control; then they should have their own account/key sense they control the use of http:BL. If they change the code and cause an abuse, only their use will be blocked.