Consolidation of studios doesn't surprise me - the cost of producing major release films has increased significantly over the last couple of decades and a lot of studios can't gamble on $200-$300 million tentpole franchise films (at least not without risking the whole farm). I've only glanced at the articles saying this combination makes sense, but they all seem to conclude that Disney would provide the "scale" necessary for Fox to compete in the current market (FWIW - Fox has one entry (Avatar) among the top 10 most expensive movie budgets, while Disney has eight). Mega-blockbuster films with huge budgets require mega-bloated companies that can finance those huge budgets. (For all those antitrust nerds playing at home, you'll recognize this "scale" as a potential "barriers to entry" argument).
Although I don't think this actually goes anywhere based on the reports, I suspect it'd survive antitrust scrutiny if it went forward (both for legal and political reasons). The closest analogy I can think of in recent memory against such a merger is the failed EchoStar/DirecTV combination in 2002 - and that was a merger of a much different sort and helped by the FCC's denial (which was the first time in decades that had happened). Fun fact - Rupert Murdoch and News Corp (which is the parent of Fox Entertainment and the studios) were instrumental in stopping that merger.
As a tangent: I saw this weekend that Disney's proposed streaming service may not include R-rated content. While a merger with Fox would give Disney many different assets and options, it'd be interesting that several of Fox's most popular franchises would be excluded from the streaming service on that basis (Aliens, Predator, and Die Hard come to mind - although I suppose Disney would just license the streaming rights for distribution).