Only I doubt Lois and Clark even quoted Bobby Bigmouth as their official source. Bobby would be what, here we call a contact (police also have this), a person who doesn't want to be quoted in articles but who often provides reliable and first class infos. No money involved, only a relation of trust between the reporter and the contact...
...Which can also raise the debate on how reliable can a source be. There has been affairs where "so called" sources used a journalist for their own purpose without her/him necessarily being aware of it...but that's another story.

Annie is right, a journalist has to consider all, or at least more than one angle or POV of a question...and it's even worse when investigation journalism is concerned. (I won't dwell on the subject, becauseyou certainly don't want a 2 pages answer here).

Back to sources...

For real hot and controversial subjects it's "the more, the better" (interviews, documents, verified pictures...). But, if the journalist only has one source he/she knows is a major reference given the subject the article is based on, he/she (the journalist, bear with me wink ) can shield his/her source by using special phrases to refer to it. There are four to six of them, each giving an indication on how close to the subject the source is.

The only drawback is that with a little crossing, other journalists can find who your real source was and cause damages by digging too far, or not in the right direction.

In the case of Bobby, Lois bases her investigation on his infos, but it's just it: a lead, a base. She has to double or triple cross it with real facts, real sources.

Carole smile1 (talk about babbling and not making sense laugh )