The only way that it would make sense for Honda to buy Nissan is if Honda got the company at a fire-sale price and was able to fire most of the workforce. From Eric Peters at ericpetersautos.com:

There are rumors afoot that Honda – which is healthy – is considering buying Nissan. Which isn’t. Just a couple of weeks ago, a senior person within Nissan’s hierarchy said the company had “12 or 14 months to survive.” That’s not healthy.
That’s just shy of dead.
Honda is not in that position. So why would Honda put itself in that position – by doing what amounts to chaining itself to a dead man walking?
Honda has been very smart so far in that it has avoided the malinvestment in battery powered devices that has left companies such as Nissan – that didn’t avoid it – with months at most to survive. It currently sells only two devices – and they are Honda-rebadged versions of another company’s devices. The “Honda” Prologue (and its Acura-badged stablemate) being in fact Chevrolet devices that General Motors mailinvested in. This means Honda won’t lose nearly as much money on the other-brand-devices it is reselling under its own brand (and for compliance reasons only). GM spent the money designing and proofing out the device that Honda tweaked a little bit cosmetically. The expensive stuff was paid for by GM.
