github/swift-style-guide — pull request #22 by dennda (2014-11-25 19:56:32+00:00)
Title: Propose not using force-unwrapping of optionals.

Pretty straightforward.

Force-unwrapping of optionals (either implicit or explicit) carries with it the risk of runtime crashes, which should be strongly avoided. There is hardly a reason to ever force-unwrap, and unless you really know what you're doing (and even then) it may go bad.

I personally try not to have a single exclamation mark in my code.