I agree that certain keywords have way too much competition that it is unrealistic for clients to expect sudden rankings on page one
hey, Promoting your site through SEO is not a bad thing at all. Infact it is a very challenging to bring your site in high rankings.
A few example of over-optimization, - Excessive link building (getting linked to crappy websites with an intent of ranking high) - Keyword stuffing (unnecessary keyword placement)
I am doing seo purely legal way, because google spider crawled every day your site & all back links of your site, if you use white hat seo tactics then this is good for our website health. if you are use black hat than google will ban your site any time.
In my opinion SEO is perfectly legal if you do it honestly. To choose keywords that represent your site is so important. In this way, users will find exactly what they are looking for in searchers. If you choose keywords that are not consistent with your product or service, the bounce rate will increase and that hurts directly to your website.