Personally, I feel that review campaign brings more results to the project owners because the participants of the review campaign will surely use the project and there is the possibility than more than 30% of the campaign participants will continue to use the project if it is a good project.
That's only true if the service meets what the reviewer wants/needs and leave positive impression to the reviewer. Meanwhile review campaign usually about newly created goods or services which usually is still "crude".
Yea and in most times it serves more than that. Search engine can also direct people to this forum to read the review of such a project depending on the keywords used.
It's not, this forum has a low index other than other sites, people can find this forum if they search about Bitcoin or use "bitcointalk" in their search engine.
Standing of this forum on search engine isn't that bad, which is why we occasionally see SEO spam. It's just Bitcointalk can't "win" against website which focus on managing SEO, which is what most website does these days.