First, yes it can be done. But...
When people say this, they're talking about getting that ranking for one keyword.
Any one keyword that you can get ranked for in 24 hours is obviously not very competitive, and while there are certainly outliers, it's more than likely to be a keyword that doesn't bring a tonne of traffic on it's own.
Can that help? Sure.
Is that ranking likely to last?
The methods people talk about to get this fast ranking are almost always to publish content on authoritative domains like ezinearticles.com or squidoo, hubpages etc, which because of their authority and frequency of crawling by the engines, mean your content there gets indexed faster, and if it's on a super low competition term, the authority of that domain name is enough to get the article/hub etc ranking on page 1.
For ezinearticles.com, this ranking is often due to the link they place to your article on their home page after you submit an article. When this link goes away after 24 hours, so does your ranking.
At Squidoo or hubpages it might remain on the front page a little longer depending on how uncompetitive the term is but the majority of the time it'll soon slide off the home page too, especially when no further work is done on it.
Even in the BEST scenario, your squid, hub, whatever, hits that front page ranking and stays there and you see a little traffic.
Do you do it again? Publishing more of your valuable unique content to a site other than your own for keyword after keyword to continue capturing those "front page rankings in 24 hours" that are only 20% of the time MAYBE going to actually stick and remain valuable for you...
AFTER WHICH I might add, that great content you wrote will be seen as originating from ezinearticles.com or squidoo.com meaning that if you publish it on your site you'll be seen as the "reprinter" and duplicater instead of the originator.
The point is, this is not a mentality or a methodology to build a business on.
Something to think about.