Negative and Positive impacts of keyword stuffing

There are way too many negatives to outweigh the positives.

The search engines are becoming increasingly smarter and keyword stuffing just doesn't work anymore.

There's only one "sort of positive" thing about black-hat stuff. It can work for a very little while until you get caught (and you will get caught) so if you like hit and run, grab people's money, get de-listed so they can't even ask for a refund, and start all over again from the beginning, then it might work for you.

Personally, I prefer building sites that Google finds acceptable, adding useful content, winning a long-term audience for my site, and making money while still being able to sleep at night without worrying about everything vanishing from the SERPs tomorrow.

I don't know what kind of mindset Black-hatters have, but it really isn't my thing. The potential gain, to me, doesn't come anywhere near compensating for the many risks.

And since I do SEO for others, I definitely wouldn't take those kinds of risks on a client's website.

And Google is getting smarter. They pay their guys BIG money to spend all day trying to catch people who are gaming the search engines. I see these kinds of techniques as being like running on a treadmill. You never get anywhere, you have to run fast to keep from falling off, and you can't ever stop running or the search engines will catch up and shut you down.

But, if you want to do it, you're responsible for your choices, and nobody here is going to be the SEO police and try to stop you. Just be smart and do some research first to see if you really think it's right for you.