Unfortunately that link doesn't lead to anything that can be used to submit this type of complaint. The categories are all wrong, and even in the general/catch-all category, the questions don't fit this type of issue.
I realize the FTC gets lots of complaints, and that some issues they deal with are more egregious than this. However, violations of this nature (but related to other products) are potentially very serious and can have repercussions for both violators' customers and competitors.
I'm the founder of an edtech startup, so that's the area where I have the most experience. There are many teacher/bloggers who have blogs where they talk about edtech tools they like. They give the appearance—both to readers, and to companies—that they're blogging/tweeting/etc. about things because they think they are effective tools for learning.
The blogs have intake forms for requesting a product review OR requesting sponsored content, but the auto-emailed response is just a rate card. Following up to ask about product reviews (and even mentioning having won major relevant awards, which indicate a review-worthy product) leads to more rate card responses. In some cases, it's pretty clear that all of the posts are bought and paid for by companies.
Some bloggers have no disclaimers to this effect (and other teachers who read the site would have no idea that sponsored content exists, since they just read the "reviews" and don't look at the pages that refer to sponsorship). Other bloggers have a generic disclaimer, at the very bottom of a sidebar (which extends so far vertically past the primary content, no one ever sees it) that says that some content is paid for. But rare is the case where the blogger actually says "This post was paid for" and "This post was not paid for"—which is precisely what teachers and parents who read the site would want to know.
I'd rather not provide links to offending sites, since I'm not anon here and don't want teacher bloggers to hate me and my company. I realize they don't make much money and need to supplement where they can (my mother and wife are educators), but there are more transparent/legal ways to do this.
This is true in every niche as far as I know. I am convinced that the vast majority of blogs that show up in search results are paid content mills and otherwise engaged in SEO operations, like paid link rings.
Based on conversations with other founders who have worked in various industries, I have had this suspicion as well. Some founders have no problem participating in the system ("it was like this with magazines—you bought advertising and then the wrote an article about you"), but others share my view and are trying to grow via different paths. Would be very interested in others' thoughts on what's worked for them!
I realize the FTC gets lots of complaints, and that some issues they deal with are more egregious than this. However, violations of this nature (but related to other products) are potentially very serious and can have repercussions for both violators' customers and competitors.