A former colleague of mine has recently started working for a certain company and sent me a link to their site. I had a look around the site, reading the different pages about the company and the services they offer. After ten minutes I gave up and asked said former colleague to tell me what his company actually did. It was impossible to tell from the website itself, which was entirely composed of unnecessarily complicated marketing blurb that seemed to practically lack all meaning in English.
The obvious question is, of course: if human beings can't tell what a company does by its website, how will the search engines? The answer is simple: they won't, and if they can't tell what the site is about, they won't be able to serve it up correctly in the search results.
If a company's website is like its virtual shop front, then a website like the example above is like a shop front with blacked out windows hidden down a quiet side street: no one would ever know it's there. Not exactly the world's best marketing strategy I'm sure you'll agree.
Traditional copywriters don't always understand search behaviour: the path people follow to ultimately end up on the site. They often concentrate on branding issues instead of SEO. Sometimes they don't even entirely understand the products or services they are supposed to promote and try to cover this up by using lots of trendy marketing terms. This is where a good SEO person should step in and make sure the basics are covered.
Being overly clever with the use of language may seem like a good idea, but using clear, plain English is more likely to both attract searchers to the site and make them convert once they're there.
Sometimes, though, it's the SEOs themselves who get carried away with the craft of making web pages noticed by search engines.
There is a lot of web content out there obviously written "by the numbers" for exactly this purpose and nothing more. It may tick all the boxes when it comes to staying on the right side of Google and co. but it's not likely to make a good impression on actual people, making it ineffective for conversion purposes.
The truth is, content that's good for SEO is not drastically different from generally well-written content. Why? Firstly, because you are never writing solely for the search engines: you are always writing first and foremost for your customers or potential customers. You may be adding content to your site to improve your search engine rankings, but it's your potential customers who'll >eventually follow the links to your site and read your blurb that's on it. If the content reads like it was written with only algorithms in mind, you may damage your brand in the long run. On the other hand, if you establish yourself as an authority or use the content as gateway pages to your products or services, you may well benefit from what originally seemed as pure SEO tactics.
In an ideal search landscape, good, informative writing should not need tweaking to be optimised. In reality, search engines are not as smart as people and will need longer blocks of text, slightly more repetition and the occasional simplification of language to make sense of a page and rank it. Keeping your content people-oriented should still be your first priority, though, and should help both searchbots and potential customers find and understand you more effectively.