Is there a Google crawling sandbox?

Many in the SEO industry must be reeling from the latest suggestion that there might be a “crawling sandbox” for some sites. The idea suggested by a well respected SEO writer, graywolf, seems plausible in the light of recent reports by a broad spectrum of webmasters who are having problems getting their pages indexed. The suggestion is that Google will not deep crawl sites if they don’t have a large enough number of backlinks, (or a high enough PR). The idea is consistent with countless anecdotal reports by webmasters whose sites have pages that have disappeared into Google’s secondary, supplemental index; and have seen their rankings fall as a result. Furthermore the idea of a crawling sandbox is also consistent with recent comments by Matt Cutts, and official Google spokesman, in a recent blog article discussing sites that likely has a “low crawl priority” because they were either involved in spammy link exchanges or didn’t have enough backlinks. It's important to realise that there’s a knock-on effect here too. As sites have their pages removed from the main index, other sites are seeing their backlink count fall, perhaps placing them in a position where their deep pages also receive a low crawl priority. For the first time in any Google algorithm update, so-called Mum and Pop sites have been hit. Mom and Pop sites are owned by people who don’t know what a backlink is, and certainly haven’t heard of SEO. All they know is that their traffic has dried up and their online sales have plummeted. If there really is a crawling sandbox, then it’s clear to us that in their efforts to prevent search engine spam, Google have got it very wrong on this algorithm update. Ironically, the simple solution to getting your site crawled and indexed would appear to be the purchase a high PR link. This must be the last thing that Google intended.