No symbols - see Bank of America !!!
Suppose I want to hack your Bank of America account. First I open an account of my own with Bank of America and then I discover that they only allow letters and numbers. This makes it much easier to hack anyone's Bank of America account - and I hope some IT guy at Bank of America who restricted passwords in this stupid way (and so made hacking easier) is reading this - or, even better, some senior official who can get this stupid policy changed.