If there's an article about his company in a legitimate publication, then he can put a page up for his company in Wikipedia. It'd pass the notability requirement and the requirement for verifiable sources.
The problem is that getting rid of the notability requirement would lead to lots of people putting up pages with nothing more than opinion. It wouldn't be spam. It'd be more dangerous than that. It'd be unsourced opinion disguised as factual information.
There's also the fact that Wikipedia is much more of a finite resource than, say, Google. Google has millions of server and a data center staff of thousands, backed up by even more thousands of programmers dedicated to making things run smoothly. Wikipedia is 400-odd servers and a staff of less than a hundred. Opening things up like you say would quickly overload Wikipedia's infrastructure, degrading the encyclopedia for everyone.