There were two times smart completion features have overtaken me. I was unable to expose the first experience, as it would violate someone else's privacy; so here comes the second experience. But this time a pretty boring one. :D
I was trying get a description of a load balancer I created. I have all the commands written down in a file. I opened it using a word processor and copied it to the terminal.
pradeeban@pradeeban:~/pem$ elb-describe-lbs autoscalelb –headers -K KEY.pem -C CERT.pem
elb-describe-lbs: Service error: LoadBalancer name cannot contain characters that are not
letters, or digits or the dash.
I was confused, where did I use an invalid character in the name (which was indeed just "autoscalelb"). After a few minutes, I figured out, it was my smart word processor, which had replaced "--headers" with "–headers" (Smart hyphenation!). :D