It's basically any niche where bad information can seriously impact your health or your finances. So medical information, credit/loan services, general financial information, anything which requires you to provide personal details.
I've seen a split in the fitness search results. Things like 'how to lose weight fast' are almost all big authority sites and/or government health information, as there's a disproportionate amount of bullshit products and services which could potentially cause harm. Searches like 'how to get a bigger bench press' are a lot more open and don't seem to be as regulated.
None of it is insurmountable though. Simple things like visible contact information, citing reputable sources in your content, having author profiles will all help. Just seems to take a little longer to rank for newer sites from what I've seen.
