No. Good, relevant content is the best. For keyword placement check your competitors and see their keyword density and how many times the keyword is mentioned. Sometimes you will be surprised it is not mentioned many times. Backlinks are much more important.
I've seen it used in blogs quite frequently, they call it a keyword cloud. The general feeling of Google as they state in their seo guidelines (i'm paraphrasing), is that your content should be well written and have a natural speech-like flow. Not to say that you can't have lists of services or products, but it is much better to have the keywords spread throughout the content than all in one block of text. It could be considered keyword stuffing and you might loose points or get blacklisted from google. You also have to keep an eye on your keyword density, a keyword to total words ratio that should not be higher than 6% for any given word or phrase. So if you need more keywords on your page add more content for each keyword you add.
Why would you want something unnatural on your site? If you write quality content, which is what Google is looking for, those keywords in your "text box full of keywords" will occur naturally if they are truly relevant to the topic of your page. Improve the quality of your content instead of trying to trick Google.
No it not beneficial for your website.It is called "Spamming" or "Stuffing".Unique Content is king.So always use unique content.And use 4 to 6 percent keyword density. ps3break