I was surprised to read this blog post from Bing Ads about how to avoid account closures. Clearly, it has come up against these situations enough times for the team to put out a message on this topic.

I'm sure the vast majority of advertisers comply, however, here's the list of the main non-compliance reasons:-

Sites that include viruses, malware, spyware, or other self-installing programs.
Business models that attempt to mislead site visitors, or that seem deceptive or fraudulent.
Sites that misrepresent the origin or intent of their content and as a result are likely to deceive a portion of the target audience.
Phishing sites that try to trick visitors into sharing personally identifiable information (PII), or where the use of such information could cause the user to be defrauded or sites that share download keys for Office, Windows and other software.
Pages that consist entirely of advertising, or whose main purpose is to direct site visitors to advertising.
Link farms.
Sites operated by advertisers who consistently violate our Editorial Policies.

o Only advertisers promoting content in violation of high risk policies, e.g. Pharmaceutical or Gambling, are at risk for account closure.

Advertisers that submit large numbers of irrelevant keywords—even if their landing pages don’t violate the Relevance and Quality policy.

o This behavior is categorized by pervasive use of completely irrelevant keywords (generally trending or popular keywords) where there is no related content available on the landing page.

Bing also goes on to explain that suspicious activity or invalid information is detected, although it doesn't elaborate on that. The account can also be blocked if the advertisers log in credentials were compromised.

[advertise.bingads.microsoft.com...]