Rules and FPS limits are set by organizers to reduce the possibility of injuries. In my experience, No limits greatly enhance the chance of injury, no matter how well intended the person shooting meant to be. No one likes getting a tooth shot out or having to remove bb's from their body and it looks like most have expressed their own feelings on the topic.
Overall, you can host your game with your own rule set. Just don't be surprised when the only ones who show up are you and your friends....
This has been my experience in the past as well.
I have always liked the higher FPS limits, but you do need limits.
Generally if you stay in the range of 375fps with .25s for full autos, and 525fps for semi-auto/bolt sniper rifles, will prompt the most people to attend your event, as it allows most all guns to be used, while keeping the injuries to a minimum.
While most people will use their common sense and play safe regardless of the rules, there will always be a few that won't give a darn and could careless if they hurt anyone (there are no rules so what I did was allowed)