Hey guys I am sure something like this has come up before but after searching for a few hours I feel like I have confused myself even more

. Essentially the scenario that I am thinking of goes something like this:
John, Bob, Billy, Zach all connect their Ethernet enabled Arduino's on different networks at their respective houses. Then they all log onto the same website that is hosted on a remote Webserver (ie..
www.thesite.com). The site would have a buttons that could control the other peoples Arduino's (turn off and on pins). Is this possible? Are there any drawbacks? Any other ways to achieve this? Or will it have to be a coding nightmare as I am afraid of?
Thanks alot I just can't find a straight answer anywhere. I am pretty sure I should look into WebClient examples on the Arduino but everything I find is all local hosts not remote. Thanks again!