Personally I wouldn't like the idea of an "interview the neighbour" type background check unless you've specifically provided that person as a reference. What would they have to gain from interviewing the mentally ill old woman next door who thinks you're Satan because you went out with a goth one time...leave that shit to the scientologists.
What if you've got holes in your paperwork anyway? I can think of several months spent backpacking and doing barwork overseas where I wouldn't have many "references" aside from passport stamps and ONE letter from the British Inland Revenue.
Criminal record checks I don't have a problem with. I had one done in order to work in a public school. Funny thing is, the previous semester I'd written a law assignment on the exact type of background check they did on ME.
To quit rambling and consider your question. As a prospective lawyer, he should have a good idea about how much he's entitled to know about how they'll be conducting their investigation. This will give him an idea on what he should tell them. Of course he'd want to be 1000 times more careful if he's actually signing an affidavit or statutory declaration.
I wouldn't go with websites, a person ready for a bar exam could probably dredge up more public record information than those sites could anyway and if those sites have private info on him that they're not meant to have maybe his first case could be to try suing THEM.
Finally, I remember reading an amusing article about doing an FOI request to see if the FBI has a record on you. The idea was; you could write and ask for your FBI file, but the very act of writing to ask for your FBI file and not having one would then trigger the creation of a brand new FBI file on you detailing that you had once asked for your FBI file. Joseph Heller eat your heart out.