2nd Qn first. It's BAD. Keyword stuffing is adding too many keywords in your page content in order to rank high in SERP. It may give your site a temporary boost; but will be detected as unnatural (blackhat) SEO practice and may lead to a ban on your site in search engines.
Keyword stuffing......... Don't do that. Its very bad for your site if you want to earn for life time from that site. But its good for temporary boost up of your website.
Of course it is not good for website optimzation, you have to utilize the keywords at very limit, you can search for the keyword stuffing trends at google for more info.
Keyword stuffing is stuffing keywords in your site so your keywords help your stuffing page get ranked for the keywords you are stuffing for. See what I did there? Think it's a good idea? Well done.
Keyword stuffing is termed as black hat seo and search engines won't prefer it. if it is been found you would be banned from search engine... see below link http://www.google.com/support/webmasters/bin/answer.py?answer=66358
Keyword stuffing is a practice that many SEO people use to do before backlinks were such a big deal. These days you page only needs about 4% keywords. Its more important to concentrate on your meta tags, title and backlinks. If you keyword stuff your page then as a user it would't look at good as a normally written page. Keep it natural.
Google is too smart for that now man don't risk it. After the Panda update they got even more strict.
Basically, you have keywords that your website is about, right? Well, Imagine writing content that has those keywords over and over. Will give your website a short lived boost in the SERPS but it won't take long for Google to catch on. Give it time. Link building and boosting your page rank is the most important thing. Just think, the majority of your traffic is always going to come from Google. so why risk blowing all of your hard work?
Keyword stuffing on web page is an unethical (black hat) search engine optimization (SEO) method. Keywords stuffing looks like this on a page: @100% of density Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword Keyword or like this: @ 30% of density Keyword lorem ipsum Keyword lorem ipsum Keyword lorem ipsum Keyword lorem ipsum Keyword lorem ipsum Keyword lorem ipsum Keyword lorem ipsum Keyword lorem ipsum Keyword lorem ipsum Keyword lorem ipsum Keyword lorem ipsum Keyword lorem ipsum Keyword lorem ipsum Keyword lorem ipsum Keyword lorem ipsum or like this: @ 15% of density Keyword lorem ipsum dolor sit amet, consectetur Keyword lorem ipsum dolor sit amet, consectetur Keyword lorem ipsum dolor sit amet, consectetur Keyword lorem ipsum dolor sit amet, consectetur Keyword lorem ipsum dolor sit amet, consectetur Keyword lorem ipsum dolor sit amet, consectetur As you can see, it produce very low quality content that has no value to readers. This technique is completely outdated and do NOT affect page rankings today, even worse - you can harm your rankings.
As stated here you really want to keep your content readable and informative to your readers. This is so true after the recent Google Panda update, so any of these sites that have employed keyword stuffing and flimsy content will all be dropping off the page soon.
Keyword stuffing has been used to obtain most search engine ranking and visibility for particular keyword. Keyword stuffing is look like black hat technique. don't use keyword stuffing, google will consider your page content as spam.
Keyword stuffing is exactly what the name suggests it to be. It is when you stuff your keywords too much into a sentence that it appears unnatural to both the SE and the human users. An example would be like in a sentence of 15 words you would use the same keyword 12 times.