Is Google indexing Spam?

Is Google treating sub-domains as full-fledged domains ?
Suddenly in a period of about six months, Google is rumored to have added another few billion pages to its index. Seems reasonable? Yes, should be at the first instance. I personally saw and monitored results from a few sites. While checking results, I discovered that while a sample site chosen for the purpose should have had about 1500 pages indexed, Google had indexed more than 3700 pages and I could see that every single page and every thing link that the page had anywhere on the net had been indexed.

While earlier, webmasters were particularly unhappy as many of their pages were not indexed on Google, now with indexing of junk pages, the problem is not going to get resolved as many spam pages appear on higher ranking. Many search results are throwing up scraped content or even the pages which once appeared as ads on another site. This is particularly bad as it means Google is not updating its data for the deleted pages or the moved content.
While Google as part of its policy is not going to reveal much on the issue, what is widely believed that Google search is now treating sub domains as independent domains and even the pages in the home page of sub-domain are again getting indexed, thus increasing the numbers of pages indexed. Some servers too are running the scripts that keep on generating pages with unique sub-domain once Google bot visits the site.
What ever be the reason, while there is a happy part in it for the webmasters that they are getting all the pages indexed, other search engines may be gaining at its cost, unless the error is rectified soon. Yahoo is soon catching up and has increased its data base index. How far yahoo would be able to strengthen its loyal customer base, would remain to be seen in next few months.