Well it's come down the government trying to push Apple into building a special version of iOS that would allow them (the government) to access data on any phone in their possession. Interesting enough, Apple has always worked with the FBI to unlock / remove data from iPhones when requested, now that doesn't seem to be enough, I'm sorry but I really don't trust the government or their security, I have a feeling this piece of software would be on the internet within days of being handed off to the feds.
Here's the letter from Tim Cook to Apple users.
http://www.apple.com/customer-letter/