Crawl Frequency

How frequently a website is crawled.

Sites which are well trusted or frequently updated may be crawled more frequently than sites with low trust scores and limited link authority. Sites with highly artificial link authority scores (ie: mostly low quality spammy links) or sites which are heavy in duplicate content or near duplicate content (such as affiliate feed sites) may be crawled less frequently than sites with unique content which are well integrated into the web.

See also:

• Google's Matt Cutts video on Google Crawling Patterns
• Matt Cutts post Indexing Timeline - mentions sites with unnatural link profiles may not be crawled as frequently or deeply