I run a small article directory, and I come across a lot of articles that are clearly written for search engines, and not to be actually read by people. This is a bad idea for many reasons.
Be Careful with Spinners
Article spinners are designed to take one article, and make it into many different versions, avoiding any duplicate content penalties that search engines might impose. Spinners aren't bad, but they are often badly used or set up. Some just appear to use a thesaurus or dictionary to automatically replace words, which can destroy the meaning of a sentence. Some words can't be simply replaced by others. Residence located enterprise, although technically the same as home based business just doesn't work.
Don't Use Walls of Text
An article that has no paragraphs or breaks is very difficult to read. Many article sites will automatically reject such hideous examples of poorly formatted text.
Search Engines are Getting Better
Search engines are becoming better able to actually recognise whether an article is written well. Poor grammar can be detected by software these days.
Don't Overuse Your Keywords
Whilst having appropriate keywords in an article, don't stuff it with so many that it just doesn't read well. You can also be penalised by search engines for having too high a keyword density.
Don't Use Irrelevant Keywords
You may be targeting a specific search phrase - often based on a locality such as a city - but don't stuff the article with that search phrase. You might be writing about litigation specialists for example, but tagging NYC onto that really has no relevance to the article itself.
Don't Use Auto-Translators
They just don't work. You get sentences composed of words just strung together that make no sense at all.
Don't Write an Advert
There's a place for articles that are essentially adverts for your business. Article directories aren't that place. Write about the type of service you offer, but don't write specifically promoting your business.
Don't Write Articles Irrelevant to your Business
Using articles to promote your business or site is good, but try to make them at least relevant. If you're writing articles for people to read, they're unlikely to click any of your resource box links if they have absolutely nothing to do with the article in question.
Now, even if you ignore all this, you will probably still get your article on some sites, but only poor-quality sites that won't be rated well in the search engines, which negates most of the benefits from writing articles and marketing online with them. You also won't get many readers, which means very few clickthroughs on any links to your site in the resource box.