Many businesses would be aghast at the idea of allowing customers to write about them and then publishing those on the official website of the business.
The world is full of people who write and publish their own content (myself included, as is evident with this very piece) and there is a wealth of un-proofed content, full of errors and inconsistencies.
Whether a comment can be considered spam is purely subjective. What is certain is the fact that any site that lets the public post content to it requires constant and careful attention.