All these translations are ethical, legal, and in full compliance with Google webmaster guidelines.
Yes, you should always translate all your articles, content, videos, presentations, anything, to another language to reach as many people as possible and to do business with as many internet users as possible.
1. You have your main website or blog
This is how you market your products or services on the internet. The website is in English but you want to reach more people.
The solution is to automatically translate the articles and to publish them on other websites or blogs that you have or even in the main blog if it has several languages. This will not harm your search engine positions and it is a great way to get more content indexed and to reach even more people.
If you have more than one social network account, trying to reach just people from China, for example, you can post all your translated content there to drive people from the foreign language social network to the foreign language website or blog to sell to that specific language speaking people who do not know English yet.
2. You can also translate foreign language articles to English and publish them on the main website or blog and this way you benefit from all the hard work you had with these secondary language websites or blogs, without having to write an entirely new article in English or to manually translate the articles.
Google Translate is the perfect tool for such a task. It works with very big articles; it is free and does not impose a limit on how many articles you can translate per day.
3. To get people to visit these newly translated articles you should use social networks such as Facebook, Twitter, and Google Plus.
On Facebook, you should have a secondary account just for internet users who speak the translated language and make friends with people interested in what you have to offer, only.
It makes no sense to make friends with people who are not interested because they will not read the post much less buy anything from you.
Marketers can try with pay-per-click advertising networks and see how lost the CTR will be with people who are not interested at the moment in buying such a product, so Facebook people work exactly the same way.
On Twitter, you should also have a separate account just for the translated articles and on Google Plus you should have a circle just for the foreign language. Finally on Stumble Upon you cannot target your audience,
so if Stumble Upon allows you to share more pages, just submit them all to Stumble Upon and see people from all countries visit your translated pages.