This is not official as expected Google will not confirm this, but I have been researching a lot on this subject and fond this to be true.
I have a number of website less then six months old still not ranked on Google and sites that are older that are. The SEO information site news have run tests on this them selves and found the same to be true.
So why they have done this we do not know but all I can guess is Google are looking for well rooted sites on the search engine.
If you want to get ranked on Google you will have to use a domain name older then one year or at a push six months old.
Do not get put off by this as there are lots of other search engines out there, we do not no if the other search engines will copy this but if they do this would not be good.
You should continue to submit to Google and run business as usual but do not full into the spam trap, what I mean by this is submitting to Google over and over as you do not see your website.
Google can ban your domain and put it into the sand pit this is something else Google will not confirm.
New sites still get a page rank you no the green bar in the tools bar but the link popularity do not seen to be right.
If you found this article of some use then that makes me happy.