Problem with Terminal after changed permission to /usr/bin
Given that you changed the read permissions on /usr/bin recursively, trying to restore the proper permissions through Terminal will not work - too many items in there have unique permissions. The best plan of action to remedy this I have is as follows.


Open Disk Utility and run Repair Permissions on your disk. This may restore the proper permissions on the files in /usr/bin.
Reboot into Recovery mode (hold the R key down during boot) and run Disk Utility there  attempting the same Repair Permissions.
If you have a Time Machine backup, restore your system from a time prior to making the permissions change. This would be accessed through Recovery mode.


Takeaway from this is never change permissions recursively on a directory unless you specifically know what you're doing.