Sometime ago, I read an article that ping on external domains, just for checking your own network connection, is not allowed and against IT laws & ethics.
So few days ago, while replying to a question on this forum, I mentioned the same thing when a user was pinging www.google.com from his personal network, but then people said it's OK to ping google.com. I am now curious to know whether it's really OK to ping google.com or yahoo.com or any other external domains from your personal network? Will not it cause any latency or load or even network related gliches to their network or servers?

Can you provide a link to the article that you read? I saw your post in the other thread and was quite surprised but the other article might put it in perspective.

Ping is a 'debugging' tool (traceroute and telnet (client) fall in this category as well) and as such it should be allowed (in my opinion); the few bytes of data that a ping adds to the load on a server can be safely ignored. If it causes glitches on a server, that server has other problems.

The problem comes when a couple of million people start pinging at the same time.

Actually since people said is okay, I am also searching for that article, but unfortunately I don't remember the reason & link where I had read that
Meanwhile, as you said minor load can be ignored, but how severe this minor load could be for such a well known domain like google, even if a thousand of people ping at a same time, we can't imagine!

Apart from this, my concerns are:-
1. How ping technically affect a remote server/domain from our local machine?
2. Is it ethical to even put a "minor load" on other's servers/domains?

It's ok to ping. That's what it was designed for. Just use it only when you need it. If you don't have any legitimate purpose in mind, then you shouldn't ping. But given that every Internet-connected PC running Microsoft Windows spews megabytes of malware to as many IPs as there are free CPU cycles available to send packets, every day the machine is powered up, I don't think many admins complain about pings. If I logged every possible IP for hits on a firewall, on my home computer, I'd have at least 100,000 per day.

I'm not positive about this, but I'm pretty sure over 50% of public IP traffic is cyber-cruft. Just be responsible and treat a computer as a privilege, not a right. It's good that you asked about it.

Ping is a poor test more and more these days. It was only designed to be a very old quick test. It tends to be blocked for many reasons or dropped. You have other tools that more directly tell you the state.