Continuing the previous theme - I recently got interested in the origin of a particular apocryphal quote attributed to a famous scientist. The quote exists in hundreds of books and tens of thousands of webpages, but the scientist in question never said it, and no one seems to know where the quote came from (sorry to be coy, I am writing this up for publication and don't want to spoil the surprise). I believe I have finally traced it to its source, and the fascinating thing is that the quote has evolved through time, gradually becoming shorter and more pithy. The most popular versions of the quote even appear to exist in several clades, or evolutionary groups. Basically it is a great illustration of Dawkins' meme concept, and one can even construct a phylogeny (evolutionary tree) of the quote using modern computational methods. This sort of thing is not entirely novel - people have traced the evolutionary history of chain-letters and Biblical manuscripts and the like - but now, we can automatically monitor the propagation and evolution of this quote on the web, rather like scientists monitor the new flu viruses as they sweep around the world each year.
The above is a trivial example, but the sky is the limit for this sort of thing. Virtually any claim made for or against some public policy or scientific hypothesis might be tracked in a similar fashion, as the claim is copied, repeated, modified, and propagated. By studying this we might learn something profound about how individuals and societies end up making decisions.
As for the second question: there is probably never a problem, or at least never an interesting problem, where a cross-disciplinary approach is inappropriate. Almost any successful scientist these days is good in a number of areas, ranging from writing to speaking to programming to math and statistics to experiment to history to field work. But this perspective may be a product of being in an evolutionary biology program.