I don't blame you for having concerns. I've heard horror stories about private gatherings, in some guy's garage, where nothing worked, people did illegal drugs and other such activities, etc.
These are not events held in some garage or basement.
The locations are safe, secure, and supervised.
They include hotel conference rooms, fire halls, and community centers.
I have yet to host a 100+ person LAN event. I have the knowledge, finances, organization, and help to do it. This is not a one time deal. If I want to hold these on a regular basis, I need to make sure that every one goes away happy. So, that means making every thing run smoothly, from the facility's electricity (i.e. not overloading circuits), to the server, to the switch(es), organization of tournaments, good food and drink, etc.
Why am I doing it? ...because more players equals more fun, and because I can :icon31:
Several months back, I received a lump sum sufficient to allow me not to work at a regular job. I am not rich, but I found myself in a position of being able to do what I like, not what ever it takes to pay the bills. These LAN events are part of what I chose to do.
If you're still not convinced, then take a look at my website.
www.LightningLAN.com
It's a work in-progress, but you should find enough information to help alleviate some of your fear.