If you are asking if someone can do a DoS attack on you in a stake and successfully kick you out then yes, it is physically possible.
I have dossed my own internet connection from a vps while on runescape just to see it work. It does.
However you cannot be dossed if
1. The person does not know your ip (cannot be learned from runescape)
2. You have your router / firewall configured to drop wan pings
3. Your internet connection down is larger than their internet connection up.
If someone wanted to ddos you they would have to get your ip from an external site or program, have a pretty good up pipe or a vps, and you have to have your firewall set to accept wan pings. If all those are true, they can ddos you out of the game.
It is real. Anyone who could actually do the it wouldn't waste their time making videos on youtube about it as they would be rolling in their billions from their guaranteed stake wins.