What would happen if someone went inside area 51?

It would depend on if the person were authorized or not. If the person were not authorized then they'd probably just get sent out. However, if that person saw something confidential then he would probably "fall off of a cliff" as the news would report not revealing his/her name. Though, some people have ended up working for the government for seeing confidential information/projects. Many hackers have ended up working as Cyber Terrorist Trackers or something related where the hackers skill would be put to use.