When SEO is done correctly it is safe and will help protect your website from future Google algorithms.
When SEO is being implemented that goes against best practices – that is when your website is put at risk.
Much of our SEO work relies on excellence in Web Development combined with Technical SEO, fundamentally this is about making your website great for visitors first, and as a by-product search engines see it as a great place to send visitors.
If a website is seen as trying to trick search engines then there are number of remedies that Google (and others) can impose. Most penalties are algorithmic but in extreme cases where a website is doing bad techniques on a consistent level, search engines will give you a manual penalty. A manual penalty could be partial for a set of keywords, for a set of pages or sitewide. A sitewide penalty will remove your entire website from the search engine completely.
Always make ask your SEO company about the risks you're taking on. This is a clear conversation we have with clients early in the campaign planning stage.