I'm not convinced that this is either workable or desirable. Not workable because it would soon become unwieldy trying to remember the network of sources from which our beliefs originate. Not desirable because it would lead to us judging the reliability of a belief by looking at the reliability of the sources, rather than by looking for some independent confirmation or refutation. Hence we would be more likely to accept something that 'everybody knows' because more sources seem to lead to higher probability.

Also, what do we do when we find that there isn't a bridge at 234567. Do we go back to each of our sources and try to persuade them that they are wrong (and that they should similarly notify their sources and anyone else that they have passed the information on to). Isn't it better to make a general announcement: Contrary to what is believed there is no bridge at 234567 (and to add the evidence to support this assertion)