It is my understanding that Google pays very little attention to a new site and that it is usually nine months to a year before you are likely to be ranked. I have read that occasionally a site that immediately posts a lot of high quality content and acquires a lot of good backlinks gets ranked sooner.
There's good reason for this. Google's only interest is in providing what searchers are looking for. If a site goes up, then is taken down a month later or doesn't demonstrate any activity, Google doesn't want to do its users a disservice by sending them to a useless site.
In short, Google wants a site to prove it's worth before I recognizes it as a useful destination.
