Really not. As a regular user you have no permission to overwrite the ls command (unless you have changed the write permissions before..?).
And regular user means a user with less privileges than root...
You really shouldn't mess around in linux as root.

By running that command as a regular user you minimize the chances of corrupting commands. Also since is appear that you're not getting an error message, it appears that that your ls command is still intact.

The cd piped to ls is not a bug. It's working correctly, but it not doing what you think it should do. Try the following (# are comment lines):

# go to home directory
cd
# run odd pipe command
cd /bin | ls
# get current directory
pwd
# re-run odd pipe command with another directory
cd /tmp | ls
# get current directory
pwd

You should get the same results for both /bin and /tmp. Changing to a valid directory produces no output to send to the pipe. ls reads arguments not from a pipe. The ls is always on the current directory. The command (although pointless) is producing the correct ouput. Better alternatives are:

cd /bin && ls
ls /bin

I agee with stickman - if you had not experimented as root, you would never have ended up in this position in the first place. Linux will protect you from damaging your system *unless* you are logged in as root. It's too late now though, there is no 'undo' function.

Perhaps the easiest option is to reinstall, and not use root unless you absolutely have to, and only when following instructions, until you are more familiar with the command line. Nearly everything can be done without needing root, apart from when you need to install new software. Never use root for day to day tasks such as reorganising your mp3 collection, browsing the web, learning new commands, etc...

It's unfortunate that you had to find this out the hard way.

Regards,
Mark.