This could very well be old news. I have no idea when these two things changed but Google has made a substantial update to both their local review policies and the “flag and fix inappropriate reviews” form and help pages.

The new “flag as inappropriate” form has more fields and is also more generic and it appears that it applies to more than just reviews:

Of more interest is the increased detail in the Local Review Policy (previously referred to as the “Review content policy“). Here is the new Local Review Policy:

Content policies

We’ll remove content that violates any of the content policies below:

• Advertising: Don’t use reviews for advertising, such as adding links to other websites or phone numbers. Reviews should be a genuine reflection of your experience with a place – don’t post reviews just to manipulate a place’s ratings.
• Spam: Please don’t spam. Write a genuine report of your experience with the place. Don’t include promotional / commercial content, and don’t post the same content multiple times.
• Phone numbers or URLs: To help prevent advertising and spammy reviews, we don’t allow phone numbers or links to other websites in reviews. If you want to add an updated number or URL for the business you’re reviewing, use the Report a problem link to report that information instead.
• Off-topic reviews: Don’t post reviews based on someone else’s experience, or that are not about the specific place you’re reviewing. Reviews aren’t meant to be a forum for general political or social commentary or personal rants. Wrong location or the place is closed? Use the Report a problem link to report that information instead of writing a review.
• Keep it clean: Don’t use obscene, profane, or offensive language. We’ll also remove reviews that represent personal attacks on others.
• Conflict of interest: Reviews are most valuable when they are honest and unbiased. If you own or work at a place, please don’t review your own business or employer. Don’t offer or accept money, products, or services to write reviews for a business or to write negative reviews about a competitor. If you’re a business owner, don’t set up review stations or kiosks at your place of business just to ask for reviews written at your place of business.
• Illegal content: Don’t post reviews that contain or link to unlawful content, like links that facilitate the sale of prescription drugs without a prescription.
• Copyrighted content: Don’t post reviews that infringe other’s rights – including copyright. For more information or to file a DMCA request, review our copyright procedures.
• Sexually Explicit Material: We don’t allow reviews that contain sexually explicit material. Also, we absolutely don’t allow reviews that sexually exploit children or present them in a sexual manner. For this type of content, we’ll remove the review, shut down the account, and send a report to the National Center for Missing & Exploited Children (NCMEC) and law enforcement.
• Impersonation: Don’t post reviews on behalf of others or misrepresent your identity or connection with the place you’re reviewing.
• Personal and confidential information: Don’t post reviews that contain another person’s personal and confidential information, including credit card information, government identification number, driver’s license information, etc.
• Hate Speech: We don’t allow reviews that advocate against groups of people based on their race or ethnic origin, religion, disability, gender, age, veteran status, sexual orientation, or gender identity.

Obviously, most of the above policies have been integrated into the review spam algo and lead to auto flagging of reviews.

Google notes on the Flag and Fix Inappropriate Reviews page that a user can get their review to show by bringing it in compliance with the above:

If a review you wrote has been flagged and removed, you can fix it yourself. Edit your review to follow our policies (for example, remove a phone number or URL link). Your review will be automatically republished.

As Priya Chandra (a rising star in the Google Business forums) points out below, Google has also made a clear and unambiguous statement about not using reviews as a forum for political or social commentary on their Tips for writing great reviews page:

Reviews not General Commentary: At times certain locations may become the subject of larger public debate or conversation due to recent news coverage or current events. While we respect and value your opinion, Local Reviews are not meant for social or political commentary. We think there are other forums that are more suited to those kinds of conversations, like blogs or social networks. Please write about your firsthand experience with the place and not general commentary on the place in relation to recent news.

Here are the review guidelines as captured in May, 2013 by the WaybackWhacky Machine:

Policy criteria for removing reviews

We want people to get ratings, reviews, and recommendations that are relevant, helpful, and trustworthy. To protect both business owners and customers, we have systems in place that may remove individual reviews that include any of the following:

• Inappropriate content: Don’t post reviews that contain or link to unlawful content, or content that violates ourGoogle+ content policy. We may also remove reviews that include plagiarism or are copied from other sites.
• Advertising and spam: Don’t use reviews for advertising or post the same or similar reviews across multiple places, don’t post fake reviews intended to boost or lower ratings, and don’t include links to other websites. For certain types of businesses that are prone to spam, we also reserve the right to prevent reviews from publicly appearing across Google.
• Off-topic reviews: Reviews should describe your personal, first-hand experience with a specific place. Don’t post reviews based on someone else’s experience, or that are not about the specific place you are reviewing. Reviews are not a forum for personal rants or crusades. Don’t use reviews to report incorrect information about a place–use theReport a problem link for that place instead.
• Conflict of interest: Reviews are only valuable when they are honest and unbiased. For instance, as a business owner or employee you should not review your own business or current place of work. Don’t offer money or product to others to write reviews for your business or write negative reviews about a competitor. We also discourage specialized review stations or kiosks set up at your place of business for the sole purpose of soliciting reviews. As a reviewer, you should not accept money or product from a business to write a review about them. Additionally, don’t feel compelled to review a certain way just because an employee of that business asked you to do so. Finally, don’t post reviews on behalf of others or misrepresent your identity or affiliation with the place you are reviewing.

Sometimes our algorithms may flag and remove legitimate reviews in our effort to combat abuse. We know this is frustrating when it happens but believe that overall, these measures are helping everyone by ensuring that the reviews appearing on Google Places are authentic, relevant, and useful.