I remember the old days of Counterstrike and the infamous "myg0t" clan who would enter CS servers and use things like wallhacks and aimbots as well as excessive deliberate teamkilling.
After they had got themselves banned from just about every server out there they launched their own "anything goes" server which could be actually be a fun experience to play on.
Another interesting thing I remember from the CS days was that me and my friends used to play the game a lot which meant that we were much more skilled than the average player. The result of this was that admins would often accuse us of cheating (we weren't) simply because our kill/death ratio was so much better than anybody elses (I used to have screenshots of myself with 40/2 kill/death ratio on public servers using pistols only).
Of course this made us pissed at the time since we kept getting banned from servers, but now I think about it where they so unjustified in doing this? Having a massive advantage over the average player whether it comes from skills or cheats still has the same affect of reducing the enjoyment of the game for average players & newbies. It's almost like having an olympic athletic squad turn up to the local school sports day and dominate every trophy.
Since I don't have as much time or interest in games as I used to when I was a teenager I tend to avoid online play in many games because the experience is generally just getting curb stomped over and over again by more experienced/obsessive players and sometimes in team based RTS games I get kicked from a team because "I don't team with noobs".
Another thing I don't understand about this is how invincibility cheats would work, I can understand things like aimbots / wallhacks because they are using information that has been pushed to the client but surely the game server should never allow something like the number of health points to be authoritative on the client end?