This had been reported on before. There are many considerations that need to be made. Being a handset manufacturer that produces feature phones and smart phones, Nokia runs much lower margins than Microsoft. If Microsoft were to buy Nokia, does this mean that Microsoft would be the sole producer of Windows Phone? If not, does this send the same confusing message that Google sent to its partners when it bought Motorola Mobility? Then there is the debt. Would Microsoft want to assume all of Nokia’s debt?

http://www.pcworld.com/article/2042470/report-microsoft-and-nokia-talked-acquisition.html