Well, mathematically, they're chopping down the search space exponentially by removing case sensitivity. People aren't going to make long, random passwords, because they can't remember them. People will typically take a word or phrase that's easy for them to remember, and muck with the case a bit, to make it much harder to guess. But if case doesn't matter, how many passwords are now just simple words? It really is a dumb decision on their part. All it does is make non-complex passwords easier to guess, which is a net loss for security, because as mentioned, if someone's got a keylogger, password complexity ceases to matter. The issue is with everyone who doesn't have a keylogger.