In theory we are but it is amazing the lengths people go to. I know that I have been approached many times by debt collectors asking about previous owners and tenants of properties I have been in. I have to be honest and say that after a while I just give them information if i have it to stop them calling or knocking on my door!
I have also heard people in local cafes and bars asking about people and its amazing how much information people will offer on a person to someone they dont know.
And of course there is the electoral roll which many companies have computerised so searching is not a case of head down going through pages and pages of data.
I also think that DP is still abused and companies are still working hand in pocket with one another but proving it is another matter.