How is that relevant? The concept doesn't require AI in order to work. Indeed, I've pointed-out elsewhere the failure of AI. So, Berners-Lee envisions AI-driven agents putting-together data from the Semantic Web.
Others of a more practical bent envision Excel putting-together data from the Semantic Web.
What is rocket-science about "this is the name of a manufacturer", "this the a manufacturer's part number", "this is a price"?
So, Berner's-Lee may have a dream that someday the President can ask an agent "how can I improve relations in the Middle East" and get a useful answer. That that day may be far away or never doesn't detract from immediatly-practical things that can be done without having to envoke rocket science.
So, pick another name for the current efforts in this direction, and let's move on.
I don't know of a law that would prevent a consumer from linking data from multiple databases. And I don't know of a law that would prevent publishers from linking publically-available data. There are laws about sharing of data of certain types - such as medical records, credit history, etc. by those who collect such data. I don't see that as being one bit of a problem. In those cases, the publisher will provide the data only to the consumer herself and to those it is authorized to share it with. The consumers electronic agent would then be free to link the data as the consumer wishes.
FWIW, these laws are already widely abused on the Internet. Anybody with a credit card can purchase a wide array of personal data. Oh, so you have to lie and check a little box saying that you obtained the consumer's permission...
It's now Standard Operating Procedure amongst small businesses and some big ones to use these services to check-up on prospective employees - with or WITHOUT their permission. For example, I've been told by the manager of a McDonald's that he checks-up on prospective employees this way. No permission is obtained, it's done on a personal credit card and turned in as an expense. Most likely not McDonald's corporate policy, but a decision of a local franchaise owner.
Given the widespread abuses by companies openly selling this information to anyone willing to pay for it, I doubt that laws about linking databases of private information are likely to give the Semantic Web much pause.
As is encryption. As is the transmission of credit-card data over the Internet. Yet, we still have e-commerce. Imagine how foolish you would feel today had you said a few years ago that selling things on the Internet and taking credit card online was impractical, because of hackers.