Basically I have a question to SEO gurus, If you can rank a 500,000 competition keyword in 10 days (which I have) is that smart or not smart. I think it's bad because It shows your site is ranking unnaturally. Your thoughts?
You're right. Take your site down IMMEDIATELY.... Seriously though, what's the problem? New pages are given a "freshness" pass. Come back in another 10 days and tell us if the site still ranks.
All will depend on what ranking strategies you have used for obtaining that rankings. Bad SEO practices like spamming with tons of crappy links or white-hat good ways to getting links from quality authority and trusted sites which search engines trust and value in a great way.
After 1 Month it's still ranking there, and I haven't touched it.. It's just an experiment. Do you think google might not see it? Or maybe they will ban it soon.
New sites do rank high in the beginning and have a tendency to drop later. It may stay though because 500,000 is really not a lot of competition these days.