Google wants to do a good job of detecting paid links. Paid links that affect search engines (whether paid text links or a paid review) can cause a site to lose trust in Google.
What is meant by paid link? I advise clients to buy sponsorships with local tech groups that offer links and logos on their websites. Would that sort of sponsored link be penalized? Why would Google penalize that? I can see it is not the same as a spontaneous link from a blog, but I don’t understand why it should be penalized.