I'm pretty sure Google doesn't really care about repetitive submissions. At worst they'll ignore them.
If not, say I was ranking in position 2 for "casino" and you were in position 1 (we wish...lol,) then what in effect you're saying that if I kept submitting your site, you would pick up a penalty and I would therefore, by default, pick up the top spot.
Google is way past those types of things having an influence on the rankings.
I also think that Renee is wrong with the sub-folders theory. Google ranks each page pretty much on it's own merits and certainly isn't going to penalise Twitter if I link to, submit or whatever,
http://www.twitter.com/doolallys
It's a valid page and Google should get the chance to know about it, and rank it or otherwise on its own merits.